Enhanced synchronization signals for coverage enhancements of low cost user equipment

ABSTRACT

A method for a user equipment (UE) in a wireless communication system is provided. The method comprises receiving, from a base station (BS), re-synchronization signals (RSSs) over a downlink channel; identifying time-domain and frequency-domain resources used for the RSSs; and identifying a set of sequences used for constructing the RSSs from the time-domain and frequency-domain resources used for the RSSs.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

The present application claims priority to: U.S. Provisional PatentApplication Ser. No. 62/476,299, filed on Mar. 24, 2017; U.S.Provisional Patent Application Ser. No. 62/479,859, filed on Mar. 31,2017; U.S. Provisional Patent Application Ser. No. 62/532,908, filed onJul. 14, 2017; U.S. Provisional Patent Application Ser. No. 62/588,006,filed on Nov. 17, 2017; and U.S. Provisional Patent Application Ser. No.62/640,360, filed on Mar. 8, 2018. The content of the above-identifiedpatent documents is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to synchronization signals inwireless communication systems and, more specifically, to thesynchronization signals for coverage enhancements of low cost UEs in anadvanced wireless communication system.

BACKGROUND

In a wireless communication network, a network access and a radioresource management (RRM) are enabled by physical layer synchronizationsignals and higher (MAC) layer procedures. In particular, a UE attemptsto detect the presence of synchronization signals along with at leastone cell identification (ID) for initial access. Once the UE is in thenetwork and associated with a serving cell, the UE monitors severalneighboring cells by attempting to detect their synchronization signalsand/or measuring the associated cell-specific reference signals (RSs).For next generation cellular systems such as third generationpartnership-new radio access or interface (3GPP-NR), efficient andunified radio resource acquisition or tracking mechanism which works forvarious use cases such as enhanced mobile broadband (eMBB), ultrareliable low latency (URLLC), massive machine type communication (mMTC),each corresponding to a different coverage requirement and frequencybands with different propagation losses is desirable. Most likelydesigned with a different network and radio resource paradigm, seamlessand low-latency RRM is also desirable.

SUMMARY

Embodiments of the present disclosure provide an NR-SS burst set designin an advanced wireless communication system.

In one embodiment, a user equipment (UE) in a wireless communicationsystem is provided. The UE includes a transceiver configured to receive,from a base station (BS), re-synchronization signals (RSSs) over adownlink channel. The UE further includes a processor operably connectedto the transceiver, the processor configured to identify time-domain andfrequency-domain resources used for the RSSs and identify a set ofsequences used for constructing the RSSs from the time-domain andfrequency-domain resources used for the RSSs.

In another embodiment, a base station (BS) in a wireless communicationsystem is provided. The BS comprises a processor configured to configuretime-domain and frequency-domain resources used for re-synchronizationsignals (RSSs), generate a set of sequences to construct the RSSs, andmap the generated set of sequences to the time-domain andfrequency-domain resources to be used for the RSSs. The BS furtherincludes a transceiver operably connected to the processor, thetransceiver configured to transmit, to a user equipment (UE), the RSSsover a downlink channel.

In yet another embodiment, a method for a user equipment (UE) in awireless communication system is provided. The method comprisesreceiving, from a base station (BS), re-synchronization signals (RSSs)over a downlink channel, identifying time-domain and frequency-domainresources to be used for the RSSs, and identifying a set of sequencesused for constructing the RSSs from the time-domain and frequency-domainresources used for the RSSs.

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “couple” and its derivativesrefer to any direct or indirect communication between two or moreelements, whether or not those elements are in physical contact with oneanother. The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller may beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items may be used,and only one item in the list may be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that in many if not most instances, such definitions apply toprior as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure;

FIG. 2 illustrates an example eNB according to embodiments of thepresent disclosure;

FIG. 3 illustrates an example UE according to embodiments of the presentdisclosure;

FIG. 4A illustrates a high-level diagram of an orthogonal frequencydivision multiple access transmit path according to embodiments of thepresent disclosure;

FIG. 4B illustrates a high-level diagram of an orthogonal frequencydivision multiple access receive path according to embodiments of thepresent disclosure;

FIG. 5 illustrates a transmitter block diagram for a PDSCH in a subframeaccording to embodiments of the present disclosure;

FIG. 6 illustrates a receiver block diagram for a PDSCH in a subframeaccording to embodiments of the present disclosure;

FIG. 7 illustrates a transmitter block diagram for a PUSCH in a subframeaccording to embodiments of the present disclosure;

FIG. 8 illustrates a receiver block diagram for a PUSCH in a subframeaccording to embodiments of the present disclosure;

FIG. 9 illustrates an example multiplexing of two slices according toembodiments of the present disclosure;

FIG. 10 illustrates an example antenna blocks according to embodimentsof the present disclosure;

FIG. 11 illustrates an example UE mobility scenario according toembodiments of the present disclosure;

FIG. 12 illustrates an example beam sweeping operation according toembodiments of the present disclosure;

FIG. 13 illustrates an example time domain positions for PSS/SSS for FDDand TDD according to embodiments of the present disclosure;

FIG. 14 illustrates an example PBCH transmitter according to embodimentsof the present disclosure;

FIG. 15 illustrates an example PBCH resource mapping according toembodiments of the present disclosure;

FIG. 16 illustrates an example CRS mapping in an RB according toembodiments of the present disclosure;

FIG. 17 illustrates an example steps for an RA process according toembodiments of the present disclosure;

FIG. 18A illustrates an example transmission of an LC-MIB according toembodiments of the present disclosure;

FIG. 18B illustrates another example transmission of an LC-MIB accordingto embodiments of the present disclosure;

FIG. 18C illustrates yet another example transmission of an LC-MIBaccording to embodiments of the present disclosure;

FIG. 18D illustrates yet another example transmission of an LC-MIBaccording to embodiments of the present disclosure;

FIG. 19A illustrates yet another example transmission of an LC-MIBaccording to embodiments of the present disclosure;

FIG. 19B illustrates yet another example transmission of an LC-MIBaccording to embodiments of the present disclosure;

FIG. 19C illustrates yet another example transmission of an LC-MIBaccording to embodiments of the present disclosure;

FIG. 19D illustrates yet another example transmission of an LC-MIBaccording to embodiments of the present disclosure;

FIG. 20A illustrates an example a transmission of enhancedsynchronization signals according to embodiments of the presentdisclosure;

FIG. 20B illustrates another example a transmission of enhancedsynchronization signals according to embodiments of the presentdisclosure;

FIG. 20C illustrates yet another example a transmission of enhancedsynchronization signals according to embodiments of the presentdisclosure; and

FIG. 20D illustrates yet another example a transmission of enhancedsynchronization signals according to embodiments of the presentdisclosure.

DETAILED DESCRIPTION

FIG. 1 through FIG. 20D, discussed below, and the various embodimentsused to describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

The following documents and standards descriptions are herebyincorporated by reference into the present disclosure as if fully setforth herein: 3GPP TS 36.211 v13.2.0, “E-UTRA, Physical channels andmodulation;” 3GPP TS 36.212 v13.2.0, “E-UTRA, Multiplexing and Channelcoding;” 3GPP TS 36.213 v13.2.0 “E-UTRA, Physical Layer Procedures;”3GPP TS 36.321 v13.2.0, “E-UTRA, Medium Access Control (MAC) protocolspecification;” and 3GPP TS 36.331 v13.2.0, “E-UTRA, Radio ResourceControl (RRC) protocol specification.”

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a “beyond 4G network” or a“post LTE system.”

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission coverage, the beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques and the like arediscussed in 5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul communication, moving network,cooperative communication, coordinated multi-points (CoMP) transmissionand reception, interference mitigation and cancellation and the like.

In the 5G system, hybrid frequency shift keying and quadrature amplitudemodulation (FQAM) and sliding window superposition coding (SWSC) as anadaptive modulation and coding (AMC) technique, and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

FIGS. 1-4B below describe various embodiments implemented in wirelesscommunications systems and with the use of orthogonal frequency divisionmultiplexing (OFDM) or orthogonal frequency division multiple access(OFDMA) communication techniques. The descriptions of FIGS. 1-3 are notmeant to imply physical or architectural limitations to the manner inwhich different embodiments may be implemented. Different embodiments ofthe present disclosure may be implemented in any suitably-arrangedcommunications system.

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure. The embodiment of the wireless network shownin FIG. 1 is for illustration only. Other embodiments of the wirelessnetwork 100 could be used without departing from the scope of thisdisclosure.

As shown in FIG. 1, the wireless network includes an eNB 101, an eNB102, and an eNB 103. The eNB 101 communicates with the eNB 102 and theeNB 103. The eNB 101 also communicates with at least one network 130,such as the Internet, a proprietary Internet Protocol (IP) network, orother data network.

The eNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe eNB 102. The first plurality of UEs includes a UE 111, which may belocated in a small business (SB); a UE 112, which may be located in anenterprise (E); a UE 113, which may be located in a WiFi hotspot (HS); aUE 114, which may be located in a first residence (R); a UE 115, whichmay be located in a second residence (R); and a UE 116, which may be amobile device (M), such as a cell phone, a wireless laptop, a wirelessPDA, or the like. The eNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe eNB 103. The second plurality of UEs includes the UE 115 and the UE116. In some embodiments, one or more of the eNBs 101-103 maycommunicate with each other and with the UEs 111-116 using 5G, LTE,LTE-A, WiMAX, WiFi, or other wireless communication techniques.

Depending on the network type, the term “base station” or “BS” can referto any component (or collection of components) configured to providewireless access to a network, such as transmit point (TP),transmit-receive point (TRP), an enhanced base station (eNodeB or eNB),a 5G base station (gNB), a macrocell, a femtocell, a WiFi access point(AP), or other wirelessly enabled devices. Base stations may providewireless access in accordance with one or more wireless communicationprotocols, e.g., 5G 3GPP new radio interface/access (NR), long termevolution (LTE), LTE advanced (LTE-A), high speed packet access (HSPA),Wi-Fi 802.11a/b/g/n/ac, etc. For the sake of convenience, the terms “BS”and “TRP” are used interchangeably in this patent document to refer tonetwork infrastructure components that provide wireless access to remoteterminals. Also, depending on the network type, the term “userequipment” or “UE” can refer to any component such as “mobile station,”“subscriber station,” “remote terminal,” “wireless terminal,” “receivepoint,” or “user device.” For the sake of convenience, the terms “userequipment” and “UE” are used in this patent document to refer to remotewireless equipment that wirelessly accesses a BS, whether the UE is amobile device (such as a mobile telephone or smartphone) or is normallyconsidered a stationary device (such as a desktop computer or vendingmachine).

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with eNBs, such as the coverage areas 120and 125, may have other shapes, including irregular shapes, dependingupon the configuration of the eNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, one or more of the UEs 111-116include circuitry, programming, or a combination thereof, for efficientcontrolling enhanced synchronization signals (RSSs) in an advancedwireless communication system. In certain embodiments, and one or moreof the eNBs 101-103 includes circuitry, programming, or a combinationthereof, for receiving efficient controlling enhanced synchronizationsignals (RSSs) in an advanced wireless communication system.

Although FIG. 1 illustrates one example of a wireless network, variouschanges may be made to FIG. 1. For example, the wireless network couldinclude any number of eNBs and any number of UEs in any suitablearrangement. Also, the eNB 101 could communicate directly with anynumber of UEs and provide those UEs with wireless broadband access tothe network 130. Similarly, each eNB 102-103 could communicate directlywith the network 130 and provide UEs with direct wireless broadbandaccess to the network 130. Further, the eNBs 101, 102, and/or 103 couldprovide access to other or additional external networks, such asexternal telephone networks or other types of data networks.

FIG. 2 illustrates an example eNB 102 according to embodiments of thepresent disclosure. The embodiment of the eNB 102 illustrated in FIG. 2is for illustration only, and the eNBs 101 and 103 of FIG. 1 could havethe same or similar configuration. However, eNBs come in a wide varietyof configurations, and FIG. 2 does not limit the scope of thisdisclosure to any particular implementation of an eNB.

As shown in FIG. 2, the eNB 102 includes multiple antennas 205 a-205 n,multiple RF transceivers 210 a-210 n, transmit (TX) processing circuitry215, and receive (RX) processing circuitry 220. The eNB 102 alsoincludes a controller/processor 225, a memory 230, and a backhaul ornetwork interface 235.

The RF transceivers 210 a-210 n receive, from the antennas 205 a-205 n,incoming RF signals, such as signals transmitted by UEs in the network100. The RF transceivers 210 a-210 n down-convert the incoming RFsignals to generate IF or baseband signals. The IF or baseband signalsare sent to the RX processing circuitry 220, which generates processedbaseband signals by filtering, decoding, and/or digitizing the basebandor IF signals. The RX processing circuitry 220 transmits the processedbaseband signals to the controller/processor 225 for further processing.

The TX processing circuitry 215 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 225. The TX processing circuitry 215 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 210 a-210 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 215 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 205 a-205 n.

The controller/processor 225 can include one or more processors or otherprocessing devices that control the overall operation of the eNB 102.For example, the controller/processor 225 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 210 a-210 n, the RX processing circuitry 220, andthe TX processing circuitry 215 in accordance with well-knownprinciples. The controller/processor 225 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. For instance, the controller/processor 225 could support beamforming or directional routing operations in which outgoing signals frommultiple antennas 205 a-205 n are weighted differently to effectivelysteer the outgoing signals in a desired direction. Any of a wide varietyof other functions could be supported in the eNB 102 by thecontroller/processor 225.

The controller/processor 225 is also capable of executing programs andother processes resident in the memory 230, such as an OS. Thecontroller/processor 225 can move data into or out of the memory 230 asrequired by an executing process.

The controller/processor 225 is also coupled to the backhaul or networkinterface 235. The backhaul or network interface 235 allows the eNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 235 could support communications overany suitable wired or wireless connection(s). For example, when the eNB102 is implemented as part of a cellular communication system (such asone supporting 5G, LTE, or LTE-A), the interface 235 could allow the eNB102 to communicate with other eNBs over a wired or wireless backhaulconnection. When the eNB 102 is implemented as an access point, theinterface 235 could allow the eNB 102 to communicate over a wired orwireless local area network or over a wired or wireless connection to alarger network (such as the Internet). The interface 235 includes anysuitable structure supporting communications over a wired or wirelessconnection, such as an Ethernet or RF transceiver.

The memory 230 is coupled to the controller/processor 225. Part of thememory 230 could include a RAM, and another part of the memory 230 couldinclude a Flash memory or other ROM.

Although FIG. 2 illustrates one example of eNB 102, various changes maybe made to FIG. 2. For example, the eNB 102 could include any number ofeach component shown in FIG. 2. As a particular example, an access pointcould include a number of interfaces 235, and the controller/processor225 could support routing functions to route data between differentnetwork addresses. As another particular example, while shown asincluding a single instance of TX processing circuitry 215 and a singleinstance of RX processing circuitry 220, the eNB 102 could includemultiple instances of each (such as one per RF transceiver). Also,various components in FIG. 2 could be combined, further subdivided, oromitted and additional components could be added according to particularneeds.

FIG. 3 illustrates an example UE 116 according to embodiments of thepresent disclosure. The embodiment of the UE 116 illustrated in FIG. 3is for illustration only, and the UEs 111-115 of FIG. 1 could have thesame or similar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 3 does not limit the scope of this disclosureto any particular implementation of a UE.

As shown in FIG. 3, the UE 116 includes an antenna 305, a radiofrequency (RF) transceiver 310, TX processing circuitry 315, amicrophone 320, and receive (RX) processing circuitry 325. The UE 116also includes a speaker 330, a processor 340, an input/output (I/O)interface (IF) 345, a touchscreen 350, a display 355, and a memory 360.The memory 360 includes an operating system (OS) 361 and one or moreapplications 362.

The RF transceiver 310 receives, from the antenna 305, an incoming RFsignal transmitted by an eNB of the network 100. The RF transceiver 310down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 325, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 325 transmits the processed basebandsignal to the speaker 330 (such as for voice data) or to the processor340 for further processing (such as for web browsing data).

The TX processing circuitry 315 receives analog or digital voice datafrom the microphone 320 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the processor 340.The TX processing circuitry 315 encodes, multiplexes, and/or digitizesthe outgoing baseband data to generate a processed baseband or IFsignal. The RF transceiver 310 receives the outgoing processed basebandor IF signal from the TX processing circuitry 315 and up-converts thebaseband or IF signal to an RF signal that is transmitted via theantenna 305.

The processor 340 can include one or more processors or other processingdevices and execute the OS 361 stored in the memory 360 in order tocontrol the overall operation of the UE 116. For example, the processor340 could control the reception of forward channel signals and thetransmission of reverse channel signals by the RF transceiver 310, theRX processing circuitry 325, and the TX processing circuitry 315 inaccordance with well-known principles. In some embodiments, theprocessor 340 includes at least one microprocessor or microcontroller.

The processor 340 is also capable of executing other processes andprograms resident in the memory 360, such as processes for CSI reportingon PUCCH. The processor 340 can move data into or out of the memory 360as required by an executing process. In some embodiments, the processor340 is configured to execute the applications 362 based on the OS 361 orin response to signals received from eNBs or an operator. The processor340 is also coupled to the I/O interface 345, which provides the UE 116with the ability to connect to other devices, such as laptop computersand handheld computers. The I/O interface 345 is the communication pathbetween these accessories and the processor 340.

The processor 340 is also coupled to the touchscreen 350 and the display355. The operator of the UE 116 can use the touchscreen 350 to enterdata into the UE 116. The display 355 may be a liquid crystal display,light emitting diode display, or other display capable of rendering textand/or at least limited graphics, such as from web sites.

The memory 360 is coupled to the processor 340. Part of the memory 360could include a random access memory (RAM), and another part of thememory 360 could include a Flash memory or other read-only memory (ROM).

Although FIG. 3 illustrates one example of UE 116, various changes maybe made to FIG. 3. For example, various components in FIG. 3 could becombined, further subdivided, or omitted and additional components couldbe added according to particular needs. As a particular example, theprocessor 340 could be divided into multiple processors, such as one ormore central processing units (CPUs) and one or more graphics processingunits (GPUs). Also, while FIG. 3 illustrates the UE 116 configured as amobile telephone or smartphone, UEs could be configured to operate asother types of mobile or stationary devices.

FIG. 4A is a high-level diagram of transmit path circuitry. For example,the transmit path circuitry may be used for an orthogonal frequencydivision multiple access (OFDMA) communication. FIG. 4B is a high-leveldiagram of receive path circuitry. For example, the receive pathcircuitry may be used for an orthogonal frequency division multipleaccess (OFDMA) communication. In FIGS. 4A and 4B, for downlinkcommunication, the transmit path circuitry may be implemented in a basestation (eNB) 102 or a relay station, and the receive path circuitry maybe implemented in a user equipment (e.g. user equipment 116 of FIG. 1).In other examples, for uplink communication, the receive path circuitry450 may be implemented in a base station (e.g. eNB 102 of FIG. 1) or arelay station, and the transmit path circuitry may be implemented in auser equipment (e.g. user equipment 116 of FIG. 1).

Transmit path circuitry comprises channel coding and modulation block405, serial-to-parallel (S-to-P) block 410, Size N Inverse Fast FourierTransform (IFFT) block 415, parallel-to-serial (P-to-S) block 420, addcyclic prefix block 425, and up-converter (UC) 430. Receive pathcircuitry 450 comprises down-converter (DC) 455, remove cyclic prefixblock 460, serial-to-parallel (S-to-P) block 465, Size N Fast FourierTransform (FFT) block 470, parallel-to-serial (P-to-S) block 475, andchannel decoding and demodulation block 480.

At least some of the components in FIGS. 4A 400 and 4B 450 may beimplemented in software, while other components may be implemented byconfigurable hardware or a mixture of software and configurablehardware. In particular, it is noted that the FFT blocks and the IFFTblocks described in this disclosure document may be implemented asconfigurable software algorithms, where the value of Size N may bemodified according to the implementation.

Furthermore, although this disclosure is directed to an embodiment thatimplements the Fast Fourier Transform and the Inverse Fast FourierTransform, this is by way of illustration only and may not be construedto limit the scope of the disclosure. It may be appreciated that in analternate embodiment of the present disclosure, the Fast FourierTransform functions and the Inverse Fast Fourier Transform functions mayeasily be replaced by discrete Fourier transform (DFT) functions andinverse discrete Fourier transform (IDFT) functions, respectively. Itmay be appreciated that for DFT and IDFT functions, the value of the Nvariable may be any integer number (i.e., 1, 4, 3, 4, etc.), while forFFT and IFFT functions, the value of the N variable may be any integernumber that is a power of two (i.e., 1, 2, 4, 8, 16, etc.).

In transmit path circuitry 400, channel coding and modulation block 405receives a set of information bits, applies coding (e.g., LDPC coding)and modulates (e.g., quadrature phase shift keying (QPSK) or quadratureamplitude modulation (QAM)) the input bits to produce a sequence offrequency-domain modulation symbols. Serial-to-parallel block 410converts (i.e., de-multiplexes) the serial modulated symbols to paralleldata to produce N parallel symbol streams where N is the IFFT/FFT sizeused in BS 102 and UE 116. Size N IFFT block 415 then performs an IFFToperation on the N parallel symbol streams to produce time-domain outputsignals. Parallel-to-serial block 420 converts (i.e., multiplexes) theparallel time-domain output symbols from Size N IFFT block 415 toproduce a serial time-domain signal. Add cyclic prefix block 425 theninserts a cyclic prefix to the time-domain signal. Finally, up-converter430 modulates (i.e., up-converts) the output of add cyclic prefix block425 to RF frequency for transmission via a wireless channel. The signalmay also be filtered at baseband before conversion to RF frequency.

The transmitted RF signal arrives at UE 116 after passing through thewireless channel, and reverse operations to those at eNB 102 areperformed. Down-converter 455 down-converts the received signal tobaseband frequency, and remove cyclic prefix block 460 removes thecyclic prefix to produce the serial time-domain baseband signal.Serial-to-parallel block 465 converts the time-domain baseband signal toparallel time-domain signals. Size N FFT block 470 then performs an FFTalgorithm to produce N parallel frequency-domain signals.Parallel-to-serial block 475 converts the parallel frequency-domainsignals to a sequence of modulated data symbols. Channel decoding anddemodulation block 480 demodulates and then decodes the modulatedsymbols to recover the original input data stream.

Each of eNBs 101-103 may implement a transmit path that is analogous totransmitting in the downlink to user equipment 111-116 and may implementa receive path that is analogous to receiving in the uplink from userequipment 111-116. Similarly, each one of user equipment 111-116 mayimplement a transmit path corresponding to the architecture fortransmitting in the uplink to eNBs 101-103 and may implement a receivepath corresponding to the architecture for receiving in the downlinkfrom eNBs 101-103.

5G communication system use cases have been identified and described.Those use cases can be roughly categorized into three different groups.In one example, enhanced mobile broadband (eMBB) is determined to dowith high bits/sec requirement, with less stringent latency andreliability requirements. In another example, ultra reliable and lowlatency (URLL) is determined with less stringent bits/sec requirement.In yet another example, massive machine type communication (mMTC) isdetermined that a number of devices can be as many as 100,000 to 1million per km2, but the reliability/throughput/latency requirementcould be less stringent. This scenario may also involve power efficiencyrequirement as well, in that the battery consumption should be minimizedas possible.

A communication system includes a Downlink (DL) that conveys signalsfrom transmission points such as Base Stations (BSs) or NodeBs to UserEquipments (UEs) and an Uplink (UL) that conveys signals from UEs toreception points such as NodeBs. A UE, also commonly referred to as aterminal or a mobile station, may be fixed or mobile and may be acellular phone, a personal computer device, or an automated device. AneNodeB, which is generally a fixed station, may also be referred to asan access point or other equivalent terminology. For LTE systems, aNodeB is often referred as an eNodeB.

In a communication system, such as LTE system, DL signals can includedata signals conveying information content, control signals conveying DLcontrol information (DCI), and reference signals (RS) that are alsoknown as pilot signals. An eNodeB transmits data information through aphysical DL shared channel (PDSCH). An eNodeB transmits DCI through aphysical DL control channel (PDCCH) or an Enhanced PDCCH (EPDCCH).

An eNodeB transmits acknowledgement information in response to datatransport block (TB) transmission from a UE in a physical hybrid ARQindicator channel (PHICH). An eNodeB transmits one or more of multipletypes of RS including a UE-common RS (CRS), a channel state informationRS (CSI-RS), or a demodulation RS (DMRS). A CRS is transmitted over a DLsystem bandwidth (BW) and can be used by UEs to obtain a channelestimate to demodulate data or control information or to performmeasurements. To reduce CRS overhead, an eNodeB may transmit a CSI-RSwith a smaller density in the time and/or frequency domain than a CRS.DMRS can be transmitted only in the BW of a respective PDSCH or EPDCCHand a UE can use the DMRS to demodulate data or control information in aPDSCH or an EPDCCH, respectively. A transmission time interval for DLchannels is referred to as a subframe and can have, for example,duration of 1 millisecond.

DL signals also include transmission of a logical channel that carriessystem control information. A BCCH is mapped to either a transportchannel referred to as a broadcast channel (BCH) when the DL signalsconvey a master information block (MIB) or to a DL shared channel(DL-SCH) when the DL signals convey a System Information Block (SIB).Most system information is included in different SIBs that aretransmitted using DL-SCH. A presence of system information on a DL-SCHin a subframe can be indicated by a transmission of a correspondingPDCCH conveying a codeword with a cyclic redundancy check (CRC)scrambled with special system information RNTI (SI-RNTI). Alternatively,scheduling information for a SIB transmission can be provided in anearlier SIB and scheduling information for the first SIB (SIB-1) can beprovided by the MIB.

DL resource allocation is performed in a unit of subframe and a group ofphysical resource blocks (PRBs). A transmission BW includes frequencyresource units referred to as resource blocks (RBs). Each RB includesN_(sc) ^(RB) sub-carriers, or resource elements (REs), such as 12 REs. Aunit of one RB over one subframe is referred to as a PRB. A UE can beallocated M_(PDSCH) RBs for a total of M_(sc) ^(PDSCH)=M_(PDSCH)·N_(sc)^(RB) REs for the PDSCH transmission BW.

UL signals can include data signals conveying data information, controlsignals conveying UL control information (UCI), and UL RS. UL RSincludes DMRS and Sounding RS (SRS). A UE transmits DMRS only in a BW ofa respective PUSCH or PUCCH. An eNodeB can use a DMRS to demodulate datasignals or UCI signals. A UE transmits SRS to provide an eNodeB with anUL CSI. A UE transmits data information or UCI through a respectivephysical UL shared channel (PUSCH) or a Physical UL control channel(PUCCH). If a UE needs to transmit data information and UCI in a same ULsubframe, it may multiplex both in a PUSCH. UCI includes HybridAutomatic Repeat request acknowledgement (HARQ-ACK) information,indicating correct (ACK) or incorrect (NACK) detection for a data TB ina PDSCH or absence of a PDCCH detection (DTX), scheduling request (SR)indicating whether a UE has data in the UE's buffer, rank indicator(RI), and channel state information (CSI) enabling an eNodeB to performlink adaptation for PDSCH transmissions to a UE. HARQ-ACK information isalso transmitted by a UE in response to a detection of a PDCCH/EPDCCHindicating a release of semi-persistently scheduled PDSCH.

An UL subframe includes two slots. Each slot includes N_(symb) ^(UL)symbols for transmitting data information, UCI, DMRS, or SRS. Afrequency resource unit of an UL system BW is a RB. A UE is allocatedN_(RB) RBs for a total of N_(RB)·N_(sc) ^(RB) REs for a transmission BW.For a PUCCH, N_(RB)=1. A last subframe symbol can be used to multiplexSRS transmissions from one or more UEs. A number of subframe symbolsthat are available for data/UCI/DMRS transmission isN_(symb)=2·(N_(symb) ^(UL)−1)−N_(SRS), where N_(SRS)=1 if a lastsubframe symbol is used to transmit SRS and N_(SRS)=0 otherwise.

FIG. 5 illustrates a transmitter block diagram 500 for a PDSCH in asubframe according to embodiments of the present disclosure. Theembodiment of the transmitter block diagram 500 illustrated in FIG. 5 isfor illustration only. FIG. 5 does not limit the scope of thisdisclosure to any particular implementation of the transmitter blockdiagram 500.

As shown in FIG. 5, information bits 510 are encoded by encoder 520,such as a turbo encoder, and modulated by modulator 530, for exampleusing quadrature phase shift keying (QPSK) modulation. A serial toparallel (S/P) converter 540 generates M modulation symbols that aresubsequently provided to a mapper 550 to be mapped to REs selected by atransmission BW selection unit 555 for an assigned PDSCH transmissionBW, unit 560 applies an Inverse fast Fourier transform (IFFT), theoutput is then serialized by a parallel to serial (P/S) converter 570 tocreate a time domain signal, filtering is applied by filter 580, and asignal transmitted 590. Additional functionalities, such as datascrambling, cyclic prefix insertion, time windowing, interleaving, andothers are well known in the art and are not shown for brevity.

FIG. 6 illustrates a receiver block diagram 600 for a PDSCH in asubframe according to embodiments of the present disclosure. Theembodiment of the diagram 600 illustrated in FIG. 6 is for illustrationonly. FIG. 6 does not limit the scope of this disclosure to anyparticular implementation of the diagram 600.

As shown in FIG. 6, a received signal 610 is filtered by filter 620, REs630 for an assigned reception BW are selected by BW selector 635, unit640 applies a fast Fourier transform (FFT), and an output is serializedby a parallel-to-serial converter 650. Subsequently, a demodulator 660coherently demodulates data symbols by applying a channel estimateobtained from a DMRS or a CRS (not shown), and a decoder 670, such as aturbo decoder, decodes the demodulated data to provide an estimate ofthe information data bits 680. Additional functionalities such astime-windowing, cyclic prefix removal, de-scrambling, channelestimation, and de-interleaving are not shown for brevity.

FIG. 7 illustrates a transmitter block diagram 700 for a PUSCH in asubframe according to embodiments of the present disclosure. Theembodiment of the block diagram 700 illustrated in FIG. 7 is forillustration only. FIG. 7 does not limit the scope of this disclosure toany particular implementation of the block diagram 700.

As shown in FIG. 7, information data bits 710 are encoded by encoder720, such as a turbo encoder, and modulated by modulator 730. A discreteFourier transform (DFT) unit 740 applies a DFT on the modulated databits, REs 750 corresponding to an assigned PUSCH transmission BW areselected by transmission BW selection unit 755, unit 760 applies an IFFTand, after a cyclic prefix insertion (not shown), filtering is appliedby filter 770 and a signal transmitted 780.

FIG. 8 illustrates a receiver block diagram 800 for a PUSCH in asubframe according to embodiments of the present disclosure. Theembodiment of the block diagram 800 illustrated in FIG. 8 is forillustration only. FIG. 8 does not limit the scope of this disclosure toany particular implementation of the block diagram 800.

As shown in FIG. 8, a received signal 810 is filtered by filter 820.Subsequently, after a cyclic prefix is removed (not shown), unit 830applies a FFT, REs 840 corresponding to an assigned PUSCH reception BWare selected by a reception BW selector 845, unit 850 applies an inverseDFT (IDFT), a demodulator 860 coherently demodulates data symbols byapplying a channel estimate obtained from a DMRS (not shown), a decoder870, such as a turbo decoder, decodes the demodulated data to provide anestimate of the information data bits 880.

In next generation cellular systems, various use cases are envisionedbeyond the capabilities of LTE system. Termed 5G or the fifth generationcellular system, a system capable of operating at sub-6 GHz and above-6GHz (for example, in mmWave regime) becomes one of the requirements. In3GPP TR 22.891, 74 5G use cases has been identified and described; thoseuse cases can be roughly categorized into three different groups. Afirst group is termed ‘enhanced mobile broadband’ (eMBB), targeted tohigh data rate services with less stringent latency and reliabilityrequirements. A second group is termed “ultra-reliable and low latency(URLL)” targeted for applications with less stringent data raterequirements, but less tolerant to latency. A third group is termed“massive MTC (mMTC)” targeted for large number of low-power deviceconnections such as 1 million per km² with less stringent thereliability, data rate, and latency requirements.

In order for the 5G network to support such diverse services withdifferent quality of services (QoS), one method has been identified inLTE specification, called network slicing. To utilize PHY resourcesefficiently and multiplex various slices (with different resourceallocation schemes, numerologies, and scheduling strategies) in DL-SCH,a flexible and self-contained frame or subframe design is utilized.

FIG. 9 illustrates an example multiplexing of two slices 900 accordingto embodiments of the present disclosure. The embodiment of themultiplexing of two slices 900 illustrated in FIG. 9 is for illustrationonly. FIG. 9 does not limit the scope of this disclosure to anyparticular implementation of the multiplexing of two slices 900.

Two exemplary instances of multiplexing two slices within a commonsubframe or frame are depicted in FIG. 9. In these exemplaryembodiments, a slice can be composed of one or two transmissioninstances where one transmission instance includes a control (CTRL)component (e.g., 920 a, 960 a, 960 b, 920 b, or 960 c) and a datacomponent (e.g., 930 a, 970 a, 970 b, 930 b, or 970 c). In embodiment910, the two slices are multiplexed in frequency domain whereas inembodiment 950, the two slices are multiplexed in time domain. These twoslices can be transmitted with different sets of numerology.

LTE specification supports up to 32 CSI-RS antenna ports which enable aneNB to be equipped with a large number of antenna elements (such as 64or 128). In this case, a plurality of antenna elements is mapped ontoone CSI-RS port. For next generation cellular systems such as 5G, themaximum number of CSI-RS ports can either remain the same or increase.

FIG. 10 illustrates an example antenna blocks 1000 according toembodiments of the present disclosure. The embodiment of the antennablocks 1000 illustrated in FIG. 10 is for illustration only. FIG. 10does not limit the scope of this disclosure to any particularimplementation of the antenna blocks 1000.

For mmWave bands, although the number of antenna elements can be largerfor a given form factor, the number of CSI-RS ports—which can correspondto the number of digitally precoded ports—tends to be limited due tohardware constraints (such as the feasibility to install a large numberof ADCs/DACs at mmWave frequencies) as illustrated in FIG. 10. In thiscase, one CSI-RS port is mapped onto a large number of antenna elementswhich can be controlled by a bank of analog phase shifters. One CSI-RSport can then correspond to one sub-array which produces a narrow analogbeam through analog beamforming. This analog beam can be configured tosweep across a wider range of angles by varying the phase shifter bankacross symbols or subframes. The number of sub-arrays (equal to thenumber of RF chains) is the same as the number of CSI-RS portsN_(CSI-PORT). A digital beamforming unit performs a linear combinationacross N_(CSI-PORT) analog beams to further increase precoding gain.While analog beams are wideband (hence not frequency-selective), digitalprecoding can be varied across frequency sub-bands or resource blocks.

In a 3GPP LTE communication system, network access and radio resourcemanagement (RRM) are enabled by physical layer synchronization signalsand higher (MAC) layer procedures. In particular, a UE attempts todetect the presence of synchronization signals along with at least onecell ID for initial access. Once the UE is in the network and associatedwith a serving cell, the UE monitors several neighboring cells byattempting to detect their synchronization signals and/or measuring theassociated cell-specific RSs (for instance, by measuring their RSRPs).For next generation cellular systems such as 3GPP NR (new radio accessor interface), efficient and unified radio resource acquisition ortracking mechanism which works for various use cases (such as eMBB,URLLC, mMTC, each corresponding to a different coverage requirement) andfrequency bands (with different propagation losses) is desirable. Mostlikely designed with a different network and radio resource paradigm,seamless and low-latency RRM is also desirable. Such goals pose at leastthe following problems in designing an access, radio resource, andmobility management framework.

First, since NR is likely to support even more diversified networktopology, the notion of cell can be redefined or replaced with anotherradio resource entity. As an example, for synchronous networks, one cellcan be associated with a plurality of TRPs (transmit-receive points)similar to a COMP (coordinated multipoint transmission) scenario in LTEspecification. In this case, seamless mobility is a desirable feature.

Second, when large antenna arrays and beamforming are utilized, definingradio resource in terms of beams (although possibly termed differently)can be a natural approach. Given that numerous beamforming architecturescan be utilized, an access, radio resource, and mobility managementframework which accommodates various beamforming architectures (or,instead, agnostic to beamforming architecture) is desirable.

FIG. 11 illustrates an example UE mobility scenario 1100 according toembodiments of the present disclosure. The embodiment of the UE mobilityscenario 1100 illustrated in FIG. 11 is for illustration only. FIG. 11does not limit the scope of this disclosure to any particularimplementation of the UE mobility scenario 1100.

For instance, the framework may be applicable for or agnostic to whetherone beam is formed for one CSI-RS port (for instance, where a pluralityof analog ports are connected to one digital port, and a plurality ofwidely separated digital ports are utilized) or one beam is formed by aplurality of CSI-RS ports. In addition, the framework may be applicablewhether beam sweeping (as illustrated in FIG. 11) is used or not.

Third, different frequency bands and use cases impose different coveragelimitations. For example, mmWave bands impose large propagation losses.Therefore, some form of coverage enhancement scheme is needed. Severalcandidates include beam sweeping (as shown in FIG. 10), repetition,diversity, and/or multi-TRP transmission. For mMTC where transmissionbandwidth is small, time-domain repetition is needed to ensuresufficient coverage.

A UE-centric access which utilizes two levels of radio resource entityis described in FIG. 11. These two levels can be termed as “cell” and“beam”. These two terms are exemplary and used for illustrativepurposes. Other terms such as radio resource (RR) 1 and 2 can also beused. Additionally, the term “beam” as a radio resource unit is to bedifferentiated with, for instance, an analog beam used for beam sweepingin FIG. 10.

As shown in FIG. 11, the first RR level (termed “cell”) applies when aUE enters a network and therefore is engaged in an initial accessprocedure. In 1110, a UE 1111 is connected to cell 1112 after performingan initial access procedure which includes detecting the presence ofsynchronization signals. Synchronization signals can be used for coarsetiming and frequency acquisitions as well as detecting the cellidentification (cell ID) associated with the serving cell. In this firstlevel, the UE observes cell boundaries as different cells can beassociated with different cell IDs. In FIG. 11, one cell is associatedwith one TRP (in general, one cell can be associated with a plurality ofTRPs). Since cell ID is a MAC layer entity, initial access involves notonly physical layer procedure(s) (such as cell search viasynchronization signal acquisition) but also MAC layer procedure(s).

The second RR level (termed “beam”) applies when a UE is alreadyconnected to a cell and hence in the network. In this second level, a UE1111 can move within the network without observing cell boundaries asillustrated in embodiment 1150. That is, UE mobility is handled on beamlevel rather than cell level, where one cell can be associated with Nbeams (N can be 1 or >1). Unlike cell, however, beam is a physical layerentity. Therefore, UE mobility management is handled solely on physicallayer. An example of UE mobility scenario based on the second level RRis given in embodiment 1150 of FIG. 11.

After the UE 1111 is associated with the serving cell 1112, the UE 1111is further associated with beam 1151. This is achieved by acquiring abeam or radio resource (RR) acquisition signal from which the UE canacquire a beam identity or identification. An example of beam or RRacquisition signal is a measurement reference signal (RS). Uponacquiring a beam (or RR) acquisition signal, the UE 1111 can report astatus to the network or an associated TRP. Examples of such reportinclude a measured beam power (or measurement RS power) or a set of atleast one recommended “beam identity (ID)” or “RR-ID”. Based on thisreport, the network or the associated TRP can assign a beam (as a radioresource) to the UE 1111 for data and control transmission. When the UE1111 moves to another cell, the boundary between the previous and thenext cells is neither observed nor visible to the UE 1111. Instead ofcell handover, the UE 1111 switches from beam 1151 to beam 1152. Such aseamless mobility is facilitated by the report from UE 711 to thenetwork or associated TRP—especially when the UE 1111 reports a set ofM>1 preferred beam identities by acquiring and measuring M beam (or RR)acquisition signals.

FIG. 12 illustrates an example beam sweeping operation 1200 according toembodiments of the present disclosure. The embodiment of the beamsweeping operation 1200 illustrated in FIG. 12 is for illustration only.FIG. 12 does not limit the scope of this disclosure to any particularimplementation of the beam sweeping operation 1200.

As shown in FIG. 12, the aforementioned initial access procedure 1210and the aforementioned mobility or radio resource management 1220 fromthe perspective of a UE are described. The initial access procedure 1210includes cell ID acquisition from DL synchronization signal(s) 1211 aswell as retrieval of broadcast information (along with systeminformation required by the UE to establish DL and UL connections)followed by UL synchronization (which can include random accessprocedure). Once the UE completes 1211 and 1212, the UE is connected tothe network and associated with a cell. Following the completion ofinitial access procedure, the UE, possibly mobile, is in an RRM statedescribed in 1220. This state includes, first, an acquisition stage 1221where the UE can periodically (repeatedly) attempt to acquire a “beam”or RR ID from a “beam” or RR acquisition signal (such as a measurementRS).

The UE can be configured with a list of beam/RR IDs to monitor. Thislist of “beam”/RR IDs can be updated or reconfigured by the TRP/network.This configuration can be signaled via higher-layer (such as RRC)signaling or a dedicated L1 or L2 control channel. Based on this list,the UE can monitor and measure a signal associated with each of thesebeam/RR IDs. This signal can correspond to a measurement RS resourcesuch as that analogous to CSI-RS resource in LTE system. In this case,the UE can be configured with a set of K>1 CSI-RS resources to monitor.Several options are possible for measurement report 1222. First, the UEcan measure each of the K CSI-RS resources, calculate a corresponding RSpower (similar to RSRP or RSRQ in LTE system), and report the RS powerto the TRP (or network). Second, the UE can measure each of the K CSI-RSresources, calculate an associated CSI (which can include CQI andpotentially other CSI parameters such as RI and PMI), and report the CSIto the TRP (or network). Based on the report from the UE, the UE isassigned M>1 “beams” or RRs either via a higher-layer (RRC) signaling oran L1/L2 control signaling 1223. Therefore the UE is connected to theseM “beams”/RRs.

For certain scenarios such as asynchronous networks, the UE can fallback to cell ID based or cell-level mobility management similar to 3GPPLTE system. Therefore, only one of the two levels of radio resourceentity (cell) is applicable. When a two-level (“cell” and “beam”) radioresource entity or management is utilized, synchronization signal(s) canbe designed primarily for initial access into the network. For mmWavesystems where analog beam sweeping (as shown in FIG. 12) or repetitionmay be used for enhancing the coverage of common signals (such assynchronization signal(s) and broadcast channel), synchronizationsignals can be repeated across time (such as across OFDM symbols orslots or subframes). This repetition factor, however, is not necessarilycorrelated to the number of supported “beams” (defined as radio resourceunits, to be differentiated with the analog beams used in beam sweeping)per cell or per TRP. Therefore, beam identification (ID) is not acquiredor detected from synchronization signal(s). Instead, beam ID is carriedby a beam (RR) acquisition signal such as measurement RS. Likewise, beam(RR) acquisition signal does not carry cell ID (hence, cell ID is notdetected from beam or RR acquisition signal).

Downlink (DL) signals include data signals conveying informationcontent, control signals conveying DL control information (DCI), andreference signals (RS), which are also known as pilot signals. A NodeBtransmits data information or DCI through respective physical DL sharedchannels (PDSCHs) or physical DL control channels (PDCCHs). A NodeBtransmits one or more of multiple types of RS including a UE-common RS(CRS), a channel state information RS (CSI-RS), and a demodulation RS(DMRS). A CRS is transmitted over a DL system bandwidth (BW) and can beused by UEs to demodulate data or control signals or to performmeasurements. To reduce CRS overhead, a NodeB may transmit a CSI-RS witha smaller density in the time and/or frequency domain than a CRS.

For interference measurement reports (IMRs), a zero power CSI-RS (ZPCSI-RS) can be used. A UE can determine CSI-RS transmission parametersthrough higher layer signaling from a NodeB. DMRS is transmitted only inthe BW of a respective PDSCH or PDCCH and a UE can use the DMRS todemodulate information in a PDSCH or PDCCH.

To assist cell search and synchronization, a cell transmitssynchronization signals such as a Primary Synchronization Signal (PSS)and a secondary synchronization Signal (SSS). Although having a samestructure, the time-domain positions of synchronization signals within aframe that includes ten subframes can differ depending on whether a cellis operating in frequency division duplex (FDD) or time division duplex(TDD). Therefore, after acquiring the synchronization signals, a UE candetermine whether a cell operates in FDD or in TDD and a subframe indexwithin a frame. The PSS and SSS occupy the central 72 sub-carriers, alsoreferred to as resource elements (REs), of an operating bandwidth.Additionally, the PSS and SSS can inform of a physical cell identifier(PCID) for a cell and therefore, after acquiring the PSS and SSS, a UEcan know the PCID of the transmitting cell.

FIG. 13 illustrates an example time domain positions 1300 for PS S/SSSfor FDD and TDD according to embodiments of the present disclosure. Theembodiment of the time domain positions 1300 illustrated in FIG. 13 isfor illustration only. FIG. 13 does not limit the scope of thisdisclosure.

Referring to FIG. 13, in case of FDD, in every frame 1305, a PSS 1325 istransmitted within a last symbol of a first slot of subframes 0 and 5(1310 and 1315), wherein a subframe includes two slots. A SSS 1320 istransmitted within a second last symbol of a same slot. In case of TDD,in every frame 1355, a PSS 1390 is transmitted within a third symbol ofsubframes 1 and 6 (1365 and 1380), while a SSS 1385 is transmitted in alast symbol of subframes 0 and 5 (1360 and 1370). The difference allowsfor the detection of the duplex scheme on a cell. The resource elementsfor PSS and SSS are not available for transmission of any other type ofDL signals.

A logical channel that carries system control information is referred toas broadcast control channel (BCCH). A BCCH is mapped to either atransport channel referred to as a broadcast channel (BCH) or to a DLshared channel (DLSCH). A BCH is mapped to a physical channel referredto as physical BCH (PBCH). A DL-SCH is mapped to PDSCH. A masterinformation block (MIB) is transmitted using BCH while other systeminformation blocks (SIBs) are provided using DL-SCH. After a UE acquiresa PCID for a cell, the UE proceeds to detect the MIB.

An MIB includes a minimal amount of system information that is neededfor a UE to receive remaining system information provided by DL-SCH.More specifically, an MIB has predefined format and includes informationof DL BW, physical hybrid-ARQ indicator channel (PHICH, 3-bit), SFN(most significant bits (MSBs) 8-bit) and 10 spare bits. A UE canindirectly acquire the two least significant bits (LSBs) of a SFN afterBCH decoding. A PBCH is transmitted using a minimum BW of 1.08 MHz inthe central part of a DL operating BW of the cell and over four SFs insuccessive frames where each SF is a first SF of a frame (see also REF1). The 40 msec timing is detected blindly without requiring explicitsignaling. Also, in each SF, a PBCH transmission is self-decodable andUEs with good channel conditions may detect a PBCH in less than fourSFs. The UE can also combine PBCH receptions in successive frames toimprove a detection probability for the MIB provided that the successiveframes convey the same MIB. In practice, this means that the successiveframes are in a same quadruple of frames and the MIB includes the sameSFN.

Most system information is included in different SIBs. An eNB transmitsSIBs using respective DL-SCHs. A presence of system information on aDL-SCH in a SF is indicated by a transmission of a corresponding PDCCHconveying a codeword with a CRC scrambled with a system information RNTI(SI-RNTI). SIB1 mainly includes information related to whether a UE isallowed to camp on a respective cell. In case of TDD, SIB1 also includesinformation about an allocation of UL/DL SFs and configuration of aspecial SF. SIB1 is transmitted in SF#5.

A set of resource blocks (RBs) in a DL BW over which SIB1 istransmitted, where each RB includes twelve consecutive REs, as well asother aspects of an associated transport format, can vary as signaled onan associated PDCCH. SIB1 also includes information about a time-domainscheduling of remaining SIBs (SIB2 and beyond). SIB2 includesinformation that UEs need to obtain in order to be able to access acell, including an UL cell BW, random-access parameters, and parametersrelated to UL power control. SIB3-SIB13 mainly includes informationrelated to cell reselection, neighboring-cell-related information,public warning messages, and so on.

FIG. 14 illustrates an example PBCH transmitter 1400 according toembodiments of the present disclosure. The embodiment of the PBCHtransmitter 1400 illustrated in FIG. 14 is for illustration only. FIG.14 does not limit the scope of this disclosure.

Referring to FIG. 14, a BCH transport block corresponding to an MIB 1410is first processed by including a 16-bit CRC 1420 followed by channelcoding 1430 using a rate-1/3 tail-biting convolutional code. Channelcoding is followed by rate matching 1440, in practice repetition of thecoded bits, and bit-level scrambling 1450. QPSK modulation 1460 is thenapplied to a coded and scrambled BCH transport block. BCH multi-antennatransmission 1470 is limited to transmitter antenna diversity in case ofmore than one transmitter antenna ports. For example, space-frequencyblock coding (SFBC) can be used in case of two antenna ports andcombined SFBC/space-frequency time diversity (FSTD) in case of fourantenna ports. By blindly detecting a transmitter antenna diversityscheme used for PBCH, a UE can determine a number of cell-specificantenna ports and also a transmitter antenna diversity scheme used forcontrol signaling. A resource mapping 1480 is finally applied and a PBCHis transmitted.

FIG. 15 illustrates an example PBCH resource mapping 1500 according toembodiments of the present disclosure. The embodiment of the PBCHresource mapping 1500 illustrated in FIG. 15 is for illustration only.FIG. 15 does not limit the scope of this disclosure.

An eNB transmits one BCH transport block, corresponding to an MIB, every40 msec or, equivalently, every 4 frames. Therefore, a BCH transmissiontime interval (TTI) is 40 msec. The eNB maps a coded BCH transport blockto a first SF 1510 of each frame in four consecutive frames 1520, 1530,1540, and 1550. A PBCH is transmitted within a first four symbols of asecond slot of SF#0 and over the 72 center REs (6 RBs) 1560. In FDD, aPBCH transmission follows immediately after a PSS and SSS transmissionin SF#0.

FIG. 16 illustrates an example CRS mapping in an RB 1600 according toembodiments of the present disclosure. The embodiment of the CRS mappingin an RB 1600 illustrated in FIG. 16 is for illustration only. FIG. 16does not limit the scope of this disclosure.

FIG. 16 illustrates a CRS mapping in a resource block (RB) that includes12 subcarriers for normal cyclic prefix (CP), where CRS can be used forchannel estimation to coherently demodulate received PBCH modulatedsymbols.

Referring to FIG. 16, for a subframe with a control region of 3 symbols1610, and a data region of 11 symbols 1620, CRS can be mapped forantenna ports 0-3, with R0-R3 (1630-1660), respectively. For the PBCHtransmission symbols in FIG. 16, the first and second symbols have CRSfor R0-R1 and R2-R3, respectively, regardless of an actual number of CRSantenna ports used by a NodeB transmitter that can be either 1, or 2, or4.

In LTE specification, the PBCH repetition was supported forbandwidth-reduced low-complexity (BL) and coverage-enhanced (CE) UEs,i.e., MTC user terminals. According to LTE specification, if a cell isconfigured with repetition of the physical broadcast channel: symbolsare mapped to core resource element (k, l) in slot 1 in subframe 0within a radio frame n_(f) according to the mapping operationaforementioned; cell-specific reference signals in OFDM symbols l inslot 1 in subframe 0 within a radio frame n_(f) with l are consideredaccording to the mapping operation aforementioned; and/or symbols areadditionally mapped to resource elements (k, l′) in slot number n′_(s)within radio frame n_(f)−i unless resource element (k, l′) is used byCSI reference signals.

The resource elements (k, l) constituting the core set of PBCH resourceelements. The mapping to resource elements (k, l) not reserved fortransmission of reference signals shall be in increasing order of firstthe index k, then the index l in slot 1 in subframe 0 and finally theradio

${k = {\frac{N_{RB}^{DL}N_{sc}^{RB}}{2} - 36 + k^{\prime}}},{k^{\prime} = 0},1,\ldots \mspace{14mu},71$

frame number. The resource-element indices are given by l=0, 1, . . . ,3 where resource elements reserved for reference signals shall beexcluded. The mapping operation shall assume cell-specific referencesignals for antenna ports 0-3 being present irrespective of the actualconfiguration. The UE shall assume that the resource elements assumed tobe reserved for reference signals in the mapping operation above but notused for transmission of reference signal are not available for PDSCH orMPDCCH transmission. The UE may not make any other assumptions aboutthese resource elements.

For frame structure type 1, l′, n′_(s), and l are given by TABLE 1A. Forframe structure type 2: if N_(RB) ^(DL)>15, l′ and n′_(s) are given byTable 1B and i=0; and if 7≤N_(RB) ^(DL)≤15, l′ and n′_(s) are given byTable 1B and i=0, except that repetitions with n′_(s)=10 and n′_(s)=11are not applied. For both frame structure type 1 and frame structuretype 2, repetition of the physical broadcast channel is not applicableif N_(RB) ^(DL)=6.

TABLE 1A Frame offset, slot and symbol number triplets for repetition ofPBCH for frame structure type 1 Frame offset, slot and symbol numbertriplets (i, n′_(s), l′) l Normal cyclic prefix Extended cyclic prefix 0(1, 18, 3), (1, 19, 0), (1, 18, 3), (1, 19, 0), (1, 19, 4), (0, 0, 4)(1, 19, 5) 1 (1, 18, 4), (1, 19, 1). (1, 18, 4), (1, 19, 1). (1, 19, 5),(0, 1, 4) (0, 0, 3) 2 (1, 18, 5), (1, 19, 2), (1, 18, 5), (1, 19, 2),(1, 19, 6), (0, 1, 5) (0, 1, 4) 3 (1, 18, 6), (1, 19, 3), (1, 19, 3),(1, 19, 4), (0, 0, 3), (0, 1, 6) (0, 1, 5)

TABLE 1B Slot and symbol number pairs for repetition of PBCH for framestructure type 2. Slot and symbol number pairs (n′_(s), l′) l Normalcyclic prefix Extended cyclic prefix 0 (0, 3), (1, 4), (10, 3), (0, 3),(10, 3), (11, 0) (11, 0), (11, 4) 1 (0, 4), (1, 5), (10, 4), (0, 4),(10, 4), (11, 1) (11, 1), (11, 5) 2 (0, 5), (10, 5), (11, 2) (0, 5),(10, 5), (11, 2) 3 (0, 6), (10, 6), (11, 3) (1, 4), (11, 3), (11, 4)

One of the fundamental requirements in an operation of a communicationsystem is a capability for a UE to request a connection setup; suchrequest is commonly referred to as random access (RA). RA is used forseveral purposes including initial access when establishing a radiolink, re-establishing a radio link after radio-link failure, handoverwhen UL synchronization needs to be established to a new cell, ULsynchronization, UE positioning based on UL measurements, and as an SRif no dedicated SR resources are configured to a UE. Acquisition of ULtiming by a serving eNB is one main objective of random access; whenestablishing an initial radio link, an RA process also serves forassigning a unique identity, referred to as cell radio network temporaryidentifier (C-RNTI), to a UE. An RA scheme can be either contentionbased (multiple UEs can use same resources) or contention-free (adedicated resource is used by a UE).

FIG. 17 illustrates an example steps for an RA 1700 process according toembodiments of the present disclosure. The embodiment of the steps foran RA 1700 process illustrated in FIG. 17 is for illustration only. FIG.17 does not limit the scope of this disclosure.

While the signaling diagram depicts a series of sequential signals,unless explicitly stated, no inference may be drawn from that sequenceregarding specific order of performance, performance of signals (orsteps) or portions thereof serially rather than concurrently or in anoverlapping manner, or performance of the signals depicted exclusivelywithout the occurrence of intervening or intermediate steps. The processin the example depicted is implemented by a transmitter chains andreceiver chains in, for example, a UE or an eNB.

As shown in FIG. 17, in step 1, a UE acquires information of physicalrandom access channel (PRACH) resources 1710 from an eNB and determinesPRACH resources for a transmission of an RA preamble 1720 (also referredto as PRACH preamble). The RA preamble is transmitted according to an RApreamble format that the eNB indicates to the UE via SIB2. In step 2,the UE receives a random access response (RAR) 1730 from the eNB. Instep 3, the UE transmits a Message 3 (Msg3) 1740 to the eNB. In step 4,the eNB and the UE perform contention resolution 1750 and a respectivemessage is referred to as message 4 (Msg4).

Contention-free random access can only be used for reestablishing ULsynchronization upon DL data arrival, handover, and positioning. Onlystep 1 and step 2 of the random access process in FIG. 17 are used asthere is no need for contention resolution in a contention-free schemewhere Step 2 can deliver C-RNTI instead of TC-RNTI

In a TDD communication system, a communication direction in some SFs ina frame is in the DL and in some other SFs is in the UL. TABLE 2provides indicative TDD UL/DL configurations over a period of a frame.In TABLE 2, “D” denotes a DL SF, “U” denotes an UL SF, and “S” denotes aspecial SF that includes a DL transmission field referred to as DwPTS, aguard period (GP), and an UL transmission field referred to as UpPTS.Several combinations exist for the duration of each field in a specialSF subject to a condition that a total duration is one SF (1 msec).

TABLE 2 TDD UL/DL configurations DL-to-UL TDD UL/DL Switch- Con- pointSF number figuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U DS U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms  DS U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D DD D 6 5 ms D S U U U D S U U D

TABLE 3 provides a special SF configuration in terms of a number ofsymbols for DwPTS, GP, and UpPTS.

TABLE 3 TDD special SF configurations DwPTS 12 11 10 9 6 3 GP 1 1 2 2 33 4 6 9 10 UpPTS 1 2 1 2 2 2 1 2 2 1

The TDD UL/DL configurations in TABLE 2 provide 40% and 90% of DL SFsper frame. Despite this flexibility, a semi-static TDD UL/DLconfiguration that can be updated every 640 msec or less frequently bysystem information (SI) signaling may not match well with short termdata traffic conditions. For this reason, faster adaptation of a TDDUL/DL configuration is considered to improve system throughputespecially for a low or moderate number of connected UEs. For example,when there is more DL traffic than UL traffic, the TDD UL/DLconfiguration may be adapted to include more DL SFs.

Signaling for faster adaptation of a TDD UL-DL configuration can beprovided by several means including a PDCCH, medium access control (MAC)signaling, and RRC signaling. An operating constraint in an adaptationof a TDD UL/DL configuration by means other than SI signaling is anexistence of UEs that cannot be aware of such adaptation. Since UEsperform measurements in DL SFs of the UL/DL configuration indicated bySI, such DL SF cannot be changed to UL SFs or to special SFs by a fasteradaptation of a TDD UL/DL configuration. However, an UL SF can bechanged to a DL SF as an eNB can ensure that UEs that are not aware ofan adapted UL/DL configuration do not transmit any signals in such ULSFs.

A DL SF can be a unicast SF or it can be a multicast-broadcast singlefrequency network (MBSFN) SF. Each DL SF (including the DwPTS of aspecial SF in case of TDD) is typically divided into a control region,consisting of first few SF symbols, and a data region consisting of aremaining SF symbols. A unicast DL SF has a control region of 1, 2, or 3symbols (or 2, 3, or 4 symbols for small DL operating bandwidths) whilean MBSFN SF has a unicast control region of one or two SF symbolsfollowed by an MBSFN region having contents that depend on a usage typefor the MBSFN SF. Information about a set of SFs configured as MBSFN SFsin a cell is provided as part of the system information.

In principle, an arbitrary pattern of MBSFN SFs can be configured with apattern repeating after 40 msec. However, SFs where informationnecessary to operate a network (specifically, synchronization signals,system information, and paging) needs to be transmitted cannot beconfigured as MBSFN SFs. Therefore, SF#0, SF#4, SF#5, and SF#9 for FDDand SF#0, SF#1, SF#5, and SF#6 for TDD are unicast SFs and cannot beconfigured as MBSFN SFs.

In time domain multiplexing (TDM) for inter-cell InterferenceCoordination (ICIC), other than regular SFs, another type of SF,referred to as almost blank SF (ABS), can be used in order to mitigateinter-cell interference. In ABS, a cell may assume that an interferingcell does not transmit signaling in all SF symbols other than the firstsymbol. Compared to a regular SF, a transmission power from aninterfering cell in an ABS can be considerably reduced. In order toobtain performance benefits from TDM-ICIC, an eNB scheduler uses ABSpatterns at interfering transmitting nodes in order to perform a linkadaptation.

In FDD, an ABS pattern is periodic with a period that is an integermultiple of 40 SFs (4 frames). In TDD, the ABS pattern period depends ona respective TDD UL-DL configuration. ABS patterns are configured andsignaled between nodes over an X2 interface or via a HeNB gateway if anX2 interface is not available. Since a period of an ABS pattern is aninteger multiple of 40 msec, X2 signaling uses a bit-map of a samelength as the ABS pattern.

Machine-type communications (MTC) through cellular networks is emergingas a significant opportunity for new applications in a networked worldwhere devices communicate with humans and with each other. Compared totypical human communication, MTC typically has relaxed latency andquality of service (QoS) requirements and often does not requiremobility support. MTC can be used for a wide variety of applications indifferent sectors including healthcare, such as monitors, industrial,such as safety and security, energy, such as meters and turbines,transport, such as fleet management and tolls, and consumer and home,such as appliances and power systems.

An important requirement for commercial success of MTC is for respectiveUEs to have low power consumption and a significantly lower cost thanconventional UEs serving human communications. Cost reduction for lowcost UEs (LC-UEs) relative to conventional UEs can be achieved, amongother simplifications, by constraining a transmission BW and a receptionBW to a small value, such as 6 RBs, of an UL system BW or a DL systemBW, respectively, by reducing a size of a data TB an LC-UE transmit orreceive, or by implementing one receiver antenna instead of the tworeceiver antennas that are implemented for conventional UEs.

LC-UEs can be installed in basements of residential buildings or,generally, in locations where an LC-UE experiences a large path-lossloss and poor coverage due to a low signal to noise and interferenceratio (SINR). LC-UE design selections of one receiver antenna andreduced maximum power amplifier gain can also result to coverage losseven when an LC-UE does not experience a large path-loss. Due to suchreasons, an LC-UE can require operation with enhanced coverage. Inextreme poor coverage scenarios, LC-UEs may have characteristics such asvery low data rate, greater delay tolerance, and limited mobility,thereby potentially being capable to operate without somemessages/channels. Not all LC-UEs require coverage enhancement (CE) orrequire a same amount of CE. In addition, in different deploymentscenarios, a required CE level can be different for different eNBs, forexample depending on an eNB transmission power or an associated cellsize or number of receiver antennas, as well as for different LC-UEs,for example depending on a location of an LC-UE.

A conventional way to support CE is to repeat transmissions of channelseither in a time domain or in a frequency domain. An LC-UE operatingwith CE can be configured by a serving ENB with one or more CE levelscorresponding to a number of SFs for transmission or reception of arespective channel. For example, an LC-UE can be configured by an eNB afirst number of SFs to receive repetitions of a PDSCH, a second numberof SFs to transmit repetitions of a PUSCH, and so on. A DL controlchannel for an LC-UE is assumed to be based on the EPDCCH structure andmay be referred to as M-PDCCH.

In order to minimize a number of SFs that an LC-UE needs to receive aPDSCH or an M-PDCCH, respective transmissions can be over all RBs theLC-UE can receive in a SF, such as in a sub-band of 6 contiguous RBs, asthe eNB is assumed to not be power limited. Conversely, as an LC-UEconfigured to transmit an UL channel with repetitions is assumed toalready transmit with a maximum power then, in order to maximize thepower spectral density, the LC-UE can transmit in 1 RB in a SF.

Further, in order to improve frequency diversity for a transmission,frequency hopping can apply where, for example, a first number ofrepetitions for the transmission are in a first sub-band and a secondnumber of repetitions for the transmission is in a second sub-band. Asthe sub-bands can correspond to different sets of 6 contiguous RBs,transmission with frequency hopping requires an LC-UE to re-tune itsRadio-Frequency (RF) to each respective sub-band and this re-tuningintroduces a delay that can range from a fraction of a SF symbol to oneSF, depending on the implementation. During a RF re-tuning period, anLC-UE is not expected to be capable of transmitting or receiving.

Transmissions of physical channels with repetitions from an LC-UE canresult to collisions with signals transmitted from conventional UEs,such as SRS, that can be configured to occur periodically andsubstantially span an UL system BW. Such collisions can destroy astructure of a signal transmission from an LC-UE and result to wastefultransmissions that unnecessarily consume UL BW and power.

Transmissions of physical channels with repetitions to or from LC-UEsneed to also avoid SFs where they can introduce interference to othertransmissions or be subject to interference from other transmissions.For example, DL transmissions to an LC-UE may be avoided in UL SFs of aTDD system or in ABS or MBSFN SFs. Therefore, there is a need to enablerepetitions for an MIB transmission to LC-UEs and for LC-UEs todetermine whether CE is supported by a serving eNB.

There is another need to determine SFs for a SIB transmission to LC-UEs.There is another need to support coexistence between repetitions for achannel transmission from an LC-UE and of SRS transmissions fromconventional UEs. Finally, there is another need to support repetitionsfor a channel transmission from or to an LC-UE in a TDD system applyingan adapted UL/DL configuration that is unknown to the LC-UE.

In the following, although the embodiments are described with referenceto BL/CE-UEs, they can also apply for conventional UEs that requirerepetitions of a DL channel or an UL channel transmission for CE.Conventional UEs can receive over the whole DL system BW and do notrequire that repetitions of a DL channel or of an UL channeltransmission in different sub-bands are in different sub-frames and donot need to have a same sub-band size as BL/CE-UEs. M-PDCCH or PDSCHtransmission to a BL/CE-UE and PUCCH or PUSCH transmissions from aBL/CE-UE are assumed to be with repetitions in a number of subframes.

An MIB for an LC-UEs is referred to as LC-MIB as it can utilize sparebits of an existing MIB to provide scheduling information for anLC-SIB-1 transmission. As an LC-UE is not aware of the UL/DLconfiguration in case of a TDD system or, in general, of ABS or MBSFNSFs when the LC-UE needs to detect the LC-MIB, an LC-MIB transmissionneeds to occur only in SFs that are guaranteed to be DL SFs regardlessof the UL/DL configuration or of the presence of ABS or MBSFN SFs. ForLC-MIB transmission, an LC-UE can assume that a conventional DL controlregion spans 3 SF symbols. This represents a maximum number of SFsymbols for the conventional DL control region for all DL system BWsexcept for small DL system BWs. However, for small DL system BWs, asonly limited DL scheduling (if any) can exist in SFs with LC-MIBtransmission, 3 SF symbols are adequate for the conventional DL controlregion without imposing adverse scheduling restrictions.

SF#0 includes the legacy PBCH (4 symbols for MIB transmission) forconventional UEs and it can also include transmission of legacy PSS andSSS for a FDD system. Then, after also excluding SF symbols for theconventional DL control region, remaining SF symbols in the middle 6 RBsare few (7 SF symbols in TDD, 5 SF symbols in FDD), and the middle 6 RBscannot be efficiently used for PDSCH or PDCCH or M-PDCCH transmissions.

In some embodiments of component V for a transmission and reception ofsynchronization signals for FDD

FIG. 18A illustrates an example transmission of an LC-MIB 1800 accordingto embodiments of the present disclosure. The embodiment of thetransmission of an LC-MIB 1800 illustrated in FIG. 18A is forillustration only. FIG. 18A does not limit the scope of this disclosure.

FIG. 18B illustrates another example transmission of an LC-MIB 1830according to embodiments of the present disclosure. The embodiment ofthe transmission of an LC-MIB 1830 illustrated in FIG. 18B is forillustration only. FIG. 18B does not limit the scope of this disclosure.

FIGS. 18A and 18B illustrate a transmission of an LC-MIB withrepetitions continuously in SF#0 and intermittently in SF#5 in a FDDsystem with a frame structure using normal CP. The MIB repetitions forLC-MIB with 1^(st), 2^(nd), 3^(rd) and 4^(th) PBCH repeated symbols arealso shown in FIGS. 18A and 18B. The SF#9 (subframe#9) includes the1^(st) and 2^(nd) PBCH repetition and part of 3^(rd) PBH repetition andthe SF#0 includes the remaining of 3^(rd) PBCH and the 4^(th) PBCHrepetition. Among the 4 symbols in each PBCH repetition, the 0^(th) PBCHsymbol and 1^(st) PBCH symbol in each PBCH repetition including the CRSREs cannot be overlapped with additional signals, which may be used forlegacy MTC UEs as well as other non-MTC UEs for cell-specific channelestimation and RRM measurement. The remaining 2^(nd) PBCH symbol and3^(rd) PBCH symbol in each PBCH repetition can be used to transmitadditional sync signals, such as enhanced PSS and/or enhanced SSS (ePSSand/or eSSS). The 2^(nd) PBCH symbol and 3^(rd) PBCH symbol in each PBCHrepetition with similar channel variation are defined as a symbol group.

There are 4 symbol groups illustrated in FIGS. 18A and 18B. Except the3^(rd) symbol group, the two symbols in other groups are adjacentsymbols. Each symbol group may be used to send repeated ePSS/eSSS andthe symbol groups are group-multiplexed with orthogonal cover codes(OCC), such as {+1, −1}. The symbol group locations can neither overlapwith CRS nor overlapped with PDCCH. The symbol group locations are notoverlapped with the legacy PSS/SSS/PBCH to avoid any impact on thenon-MTC UEs.

For example, 1^(St) symbol group with the frame offset, slot and symbolnumber triplets (i, n′_(s), l′) as (1, 18, 5) and (1, 18, 6); 2^(nd)symbol group with the frame offset, slot and symbol number triplets (i,n′_(s), l′) as (1, 19, 2) and (1, 19, 3); 3^(rd) symbol group with theframe offset, slot and symbol number triplets (i, n′_(s), l′) as (1, 19,6) and (0, 0, 3); 4^(th) symbol group with the frame offset, slot andsymbol number triplets (i, n′_(s), l′) as (0, 1, 5) and (0, 1, 6). Inone sub-embodiment, ePSS in 1^(st), 2^(nd), 3^(rd) and 4^(th) symbolgroups multiplexed with {+1, −1, +1, −1} OCC is repeated, respectively.

The ePSS sequence length can be same as that of legacy PSS sequence. Aspecial case is to use the Zadoff-Chu (ZC) sequence with length of 63and root of 38, which is conjugate of ZC sequence PSS with root of 25.Another example is to a longer sequence for ePSS with 2 times that oflegacy PSS to achieve better correlation characteristics. The longersequence is mapped into two symbols within a symbol group. To combinethe 2^(nd) PBCH symbol and 3^(rd) PBCH symbol in the 4-time PBCHrepetitions respectively (symbol-level combining) can cancel theinterference of the overlapped additional ePSS symbol due to the OCC.For ePSS detection, the MTC UEs may first de-scramble the OCC for eachsymbol group and combine the ePSS signals. The PBCH signals areorthogonal to the ePSS signals.

In another sub-embodiment, eSSS in 1^(st), 2^(nd), 3^(rd) and 4^(th)symbol groups multiplexed with {+1, −1, +1, −1} OCC is repeated,respectively. eSSS sequence can be same as legacy SSS sequence. In oneexample, a longer sequence for eSSS with 2 times that of legacy SSS toachieve better correlation characteristics is considered. The longersequence is mapped into two symbols within a symbol group. To combinethe 2^(nd) PBCH symbol and 3^(rd) PBCH symbol in the 4-time PBCHrepetitions respectively (symbol-level combining) can cancel theinterference of the overlapped additional eSSS symbol due to the OCC.For eSSS detection, the MTC UEs may first de-scramble the OCC for eachsymbol group and combine the eSSS signals. The PBCH signals areorthogonal to the eSSS signals.

In another sub-embodiment, ePSS in 1^(st), 2^(nd) symbol groupmultiplexed with {+1, −1} OCC, respectively is considered, and eSSS in3^(rd) and 4^(th) symbol groups multiplexed with {+1, −1} is repeated.The ePSS sequence length can be same as that of legacy PSS sequence or alonger sequence for ePSS with 2 times that of legacy PSS to achievebetter correlation characteristics. A special case is to use theZadoff-Chu (ZC) sequence with length of 63 and root of 38, which isconjugate of ZC sequence PSS with root of 25. Similarly the eSSSsequence can be same as legacy SSS sequence or a longer sequence foreSSS with 2 times that of legacy SSS to achieve better correlationcharacteristics.

To combine the 2^(nd) PBCH symbol and 3^(rd) PBCH symbol in the 4-timePBCH repetitions respectively (symbol-level combining) can cancel theinterference of the overlapped additional ePSS in 1^(st) and 2^(nd)symbol group as well as the eSSS in 3^(rd) and 4^(th) symbol group dueto the OCC. For ePSS detection, the MTC UEs may first de-scramble theOCC for 1^(st) and 2^(nd) symbol group and combine the ePSS signals. ForeSSS detection, the MTC UEs may first de-scramble the OCC for 3^(rd) and4^(th) symbol group and combine the eSSS signals. The PBCH signals areorthogonal to the ePSS/eSSS signals. Note that the ePSS repetition andeSSS repetition can be applied separately. For example, only the ePSS in1^(st), 2^(nd) symbol group multiplexed with {+1, −1} OCC but noadditional eSSS repetition on in 3^(rd) and 4^(th) symbol groups. Foranother example, only the eSSS in 3^(rd) and 4^(th) symbol groupmultiplexed with {+1, −1} OCC but no additional ePSS repetition 2nd onin 1^(st), 2^(nd) symbol groups.

In another sub-embodiment, eSSS in 1^(st), 2^(nd) symbol groupmultiplexed with {+1, −1} OCC is repeated, respectively, and ePSS in3^(rd) and 4^(th) symbol groups multiplexed with {+1, −1} is repeated.The eSSS sequence can be same as legacy SSS sequence or a longersequence for eSSS with 2 times that of legacy SSS to achieve bettercorrelation characteristics. Similarly the ePSS sequence length can besame as that of a legacy PSS sequence or a longer sequence for ePSS with2 times that of legacy PSS to achieve better correlationcharacteristics.

A special case is to use the Zadoff-Chu (ZC) sequence with length of 63and root of 38, which is conjugate of ZC sequence PSS with root of 25.To combine the 2^(nd) PBCH symbol and 3^(rd) PBCH symbol in the 4-timePBCH repetitions respectively (symbol-level combining) can cancel theinterference of the overlapped additional eSSS in 1^(st) and 2^(nd)symbol group as well as the ePSS in 3^(rd) and 4^(th) symbol group dueto the OCC. For eSSS detection, the MTC UEs may first de-scramble theOCC for 1^(st) and 2^(nd) symbol group and combine the eSSS signals. ForePSS detection, the MTC UEs may first de-scramble the OCC for 3^(rd) and4^(th) symbol group and combine the ePSS signals. The PBCH signals areorthogonal to the ePSS/eSSS signals.

Note that the eSSS repetition and ePSS repetition can be appliedseparately. For example, only the eSSS in 1^(st), 2^(nd) symbol groupmultiplexed with {+1, −1} OCC but no additional ePSS repetition on in3^(rd) and 4^(th) symbol groups. For another example, only the ePSS in3^(rd) and 4^(th) symbol group multiplexed with {+1, −1} OCC but noadditional eSSS repetition on in 1^(st), 2^(nd) symbol groups.

In another sub-embodiment, ePSS in the 1^(st) symbol of 1^(st), 2^(nd),3^(rd) and 4^(th) symbol groups multiplexed with {+1, −1, +1, −1} OCC isrepeated, respectively. ePSS sequence length can be same as that oflegacy PSS sequence. A special case is to use the Zadoff-Chu (ZC)sequence with length of 63 and root of 38, which is conjugate of ZCsequence PSS with root of 25. And eSSS in the 2^(nd) symbol of 1^(st),2^(nd), 3^(rd) and 4^(th) symbol groups multiplexed with {+1, −1, +1,−1} OCC is repeated, respectively.

To combine the 2^(nd) PBCH symbol in the 4-time PBCH repetitions(symbol-level combining) can cancel the interference of the overlappedadditional ePSS symbol due to the OCC. For ePSS detection, the MTC UEsmay first de-scramble the OCC for each symbol group and combine the ePSSsignals. The PBCH signals are orthogonal to the ePSS signals. To combinethe 3^(rd) PBCH symbol in the 4-time PBCH repetitions (symbol-levelcombining) can cancel the interference of the overlapped additional eSSSsymbol due to the OCC. For eSSS detection, the MTC UEs may firstde-scramble the OCC for each symbol group and combine the eSSS signals.The PBCH signals are orthogonal to the eSSS signals. The ePSS and eSSSsymbol can be shifted within each symbol group but all the symbol groupshas same order of ePSS and eSSS.

Note that the similar concept can be extended for FDD frame structurewith extended CP (ECP).

FIG. 18C illustrates yet another example transmission of an LC-MIB 1850according to embodiments of the present disclosure. The embodiment ofthe transmission of an LC-MIB 1850 illustrated in FIG. 18C is forillustration only. FIG. 18C does not limit the scope of this disclosure.

FIG. 18D illustrates yet another example transmission of an LC-MIB 1870according to embodiments of the present disclosure. The embodiment ofthe transmission of an LC-MIB 1870 illustrated in FIG. 18D is forillustration only. FIG. 18D does not limit the scope of this disclosure.

FIGS. 18C and 18D illustrate some other sub-embodiments of atransmission of an LC-MIB with repetitions continuously in SF#0 andintermittently in SF#5 in a FDD system with a frame structure usingnormal CP. The MIB repetitions for LC-MIB with 1^(st), 2^(nd), 3^(rd)and 4^(th) PBCH repeated symbols are also shown in FIGS. 18C and 18D.The SF#9 (subframe#9) includes the 1^(st) and 2^(nd) PBCH repetition andpart of 3^(rd) PBH repetition and the SF#0 includes the remaining of3^(rd) PBCH and the 4^(th) PBCH repetition. Among the 4 symbols in eachPBCH repetition, the CRS REs or CRS copy REs in the 0^(th) PBCH symboland 1^(st) PBCH symbol per PBCH repetition cannot be overlapped withadditional signals, which may be used for legacy MTC UEs as well asother non-MTC UEs for cell-specific channel estimation and RRMmeasurement.

The corresponding REs in the 0^(th) and 1^(st) symbol per groupoverlapping with legacy CRS REs may be punctured to avoid the impact onCRS reception at the price of the correlation performance of additionalsignals, such as ePSS and/or eSSS. The symbols in each PBCH repetitionwith similar channel variation are: defined as a symbol group, There are4 symbols per group illustrated in FIGS. 18C and 18I). The 1^(st) and2^(nd) symbol groups have consecutive symbols but the 3^(rd) and 4^(th)symbol groups have non-consecutive symbols. Each symbol group may beused to send repeated ePSS/eSSS and the symbol groups aregroup-multiplexed with orthogonal cover codes (OCC), such as {+1, −}.Other orthogonal codes, e.g., P-matrix, Hadama codes, are also possible.The symbol group locations are neither overlapped with PDCCH, noroverlapped with the legacy PSS/SSS/PBCH to avoid any impact on thenon-MTC UEs.

For example, 1^(st) symbol group with the frame offset, slot and symbolnumber triplets (i, n′_(s), l′) as (1, 18, 3), (1, 18, 4), (1, 18, 5)and (1, 18, 6); 2^(nd) symbol group with the frame offset, slot andsymbol number triplets (i, n′_(s), l′) as (1, 19, 0), (1, 19, 1), (1,19, 2) and (1, 19, 3); 3^(rd) symbol group with the frame offset, slotand symbol number triplets (i, n′_(s), l′) as (1, 19, 4), (1, 19, 5),(1, 19, 6) and (0, 0, 3); and 4^(th) symbol group with the frame offset,slot and symbol number triplets (i, n′_(s), l′) as (0, 0, 4), (0, 1, 4),(0, 1, 5) and (0, 1, 6).

In one sub-embodiment, ePSS in the 2^(nd) and 3^(rd) symbols of 1^(st),2^(nd), 3^(rd) and 4^(th) symbol groups multiplexed with cover codes,such as {+1, −1, +1, −1} OCC, is repeated, respectively. The ePSSlocation with the frame offset, slot and symbol number triplets (i,n′_(s), l′) are (1, 18, 5), (1, 18, 6), (1, 19, 2), (1, 19, 3), (1, 19,6), (0, 0, 3), (0, 0, 4) and (0, 1, 4). To let UE differentiate ePSS andlegacy PSS, a new sequence is designed for ePSS. The ePSS sequencelength can be same as that of legacy PSS sequence. A special case is touse the Zadoff-Chu (ZC) sequence with length of 63 and root of 38, whichis conjugate of ZC sequence PSS with root of 25.

Since ePSS on the symbols without CRS does not need puncturing infrequency domain, the time-domain sequence correlation with the ZCsequence conjugate with that of PSS is simple from implementation pointof view. Or the ePSS is a longer sequence around 2 times that of legacyPSS. To combine the 2^(nd) and 3^(rd) PBCH symbols in the 4-time PBCHrepetitions (symbol-level combining) can cancel the interference of theoverlapped additional ePSS symbol due to the orthogonality of covercodes. For ePSS detection, the MTC UEs may firstly de-scramble the OCCfor each symbol group and combine the ePSS signals.

The PBCH signals are orthogonal to the ePSS signals. In addition to ePSSrepetition, the eSSS is repeated in the 0^(th) and 1^(st) symbols of1^(st), 2^(nd), 3^(rd) and 4^(th) symbol groups multiplexed with {+1,−1, +1, −1} OCC, respectively. The eSSS location with the frame offset,slot and symbol number triplets (i, n′_(s), l′) are (1, 18, 3), (1, 18,4), (1, 19, 0), (1, 19, 1), (1, 19, 4), (1, 19, 5), (0, 1, 5) and (0, 1,6). The SSS sequence can be reused for eSSS. But eSSS on CRS REs needspuncturing in frequency domain. To combine the 0^(th) and 1^(st) PBCHsymbol in the 4-time PBCH repetitions (symbol-level combining) cancancel the interference of the overlapped additional eSSS symbol due tothe orthogonality of cover codes. For eSSS detection, the MTC UEs mayfirst de-scramble the cover codes for each symbol group and combine theeSSS signals. The PBCH signals are orthogonal to the eSSS signals.

In another sub-embodiment, ePSS in the 0^(th) and 1^(st) symbols of1^(st), 2^(nd), 3^(rd), and 4^(th) symbol groups multiplexed with covercodes, such as {+1, −1, +1, −1} OCC, is repeated, respectively. The ePSSlocation with the frame offset, slot and symbol number triplets (i,n′_(s), l′) are (1, 18, 3), (1, 18, 4), (1, 19, 0), (1, 19, 1), (1, 19,4), (1, 19, 5), (0, 1, 5) and (0, 1, 6). The ePSS can be a shortsequence with similar length of legacy PSS length. Or the ePSS is alonger sequence around 2 times that of legacy PSS. But ePSS on CRS REsneeds puncturing in frequency domain. To combine the 0^(th) and 1^(st)PBCH symbols in the 4-time PBCH repetitions (symbol-level combining) cancancel the interference of the overlapped additional ePSS symbol due tothe orthogonality of cover codes.

For ePSS detection, the MTC UEs may firstly de-scramble the OCC for eachsymbol group and combine the ePSS signals. The PBCH signals areorthogonal to the ePSS signals. In addition to ePSS repetition, the eSSSis repeated in the 2^(nd) and 3^(rd) symbols of 1^(st), 2^(nd), 3^(rd)and 4^(th) symbol groups multiplexed with {+1, −1, +1, −1} OCC,respectively. The eSSS location with the frame offset, slot and symbolnumber triplets (i, n′_(s), l′) are (1, 18, 5), (1, 18, 6), (1, 19, 2),(1, 19, 3), (1, 19, 6), (0, 0, 3), (0, 0, 4) and (0, 1, 4). The SSSsequence can be reused for eSSS.

To combine the 2^(nd) and 3^(rd) PBCH symbol in the 4-time PBCHrepetitions (symbol-level combining) can cancel the interference of theoverlapped additional eSSS symbol due to the orthogonality of covercodes. For eSSS detection, the MTC UEs may first de-scramble the covercodes for each symbol group and combine the eSSS signals. The PBCHsignals are orthogonal to the eSSS signals.

In another sub-embodiment, ePSS in 1^(st), 2^(nd) symbol groupmultiplexed with cover code, such as {+1, −1} OCC, is repeated,respectively. And repeat eSSS in 3^(rd) and 4^(th) symbol groupsmultiplexed with {+1, −1}. The ePSS location with the frame offset, slotand symbol number triplets (i, n′_(s), l′) are (1, 18, 3), (1, 18, 4),(1, 18, 5), (1, 18, 6), (1, 19, 0), (1, 19, 1), (1, 19, 2), and (1, 19,3). The eSSS location with the frame offset, slot and symbol numbertriplets (i, n′_(s), l′) are (1, 19, 4), (1, 19, 5), (1, 19, 6), (0, 0,3), (0, 0, 4), (0, 1, 4), (0, 1, 5) and (0, 1, 6). The ePSS sequence canbe symbol-level with similar length of legacy PSS sequence. Or the ePSSis a longer sequence with longer length around 2 or 4 times that oflegacy PSS.). The SSS sequence can be reused for eSSS. But ePSS as wellas eSSS on CRS REs needs puncturing in frequency domain.

For ePSS detection, the MTC UEs may first de-scramble the cover codesfor 1^(st) and 2^(nd) symbol group and combine the ePSS signals. Tocombine the PBCH symbol with same symbol index in the 2-time PBCHrepetitions respectively (symbol-level combining) can cancel theinterference of the overlapped additional ePSS in 1^(st) and 2^(nd)symbol groups. Similar procedure as eSSS combining in the 3^(rd) and4^(th) symbol group. Note that the ePSS repetition and eSSS repetitioncan also be applied separately. For example, only the ePSS in 1^(st),2^(nd) symbol group multiplexed with {+1, −1} OCC but no additional eSSSrepetition on in 3^(rd) and 4^(th) symbol groups. For another example,only the eSSS in 3^(rd) and 4^(th) symbol group multiplexed with {+1,−1} OCC but no additional ePSS repetition on in 1^(st), 2^(nd) symbolgroups.

In another sub-embodiment, eSSS in 1^(st), 2^(nd) symbol groupmultiplexed with cover code, such as {+1, −1} OCC, is repeated,respectively. And repeat ePSS in 3^(rd) and 4^(th) symbol groupsmultiplexed with {+1, −1}. The eSSS location with the frame offset, slotand symbol number triplets (i, n′_(s), l′) are (1, 18, 3), (1, 18, 4),(1, 18, 5), (1, 18, 6), (1, 19, 0), (1, 19, 1), (1, 19, 2), and (1, 19,3). The ePSS location with the frame offset, slot and symbol numbertriplets (i, n′_(s), l′) are (1, 19, 4), (1, 19, 5), (1, 19, 6), (0, 0,3), (0, 0, 4), (0, 1, 4), (0, 1, 5) and (0, 1, 6).

The ePSS sequence can be symbol-level with similar length of legacy PSSsequence. Or the ePSS is a longer sequence with longer length around 2or 4 times that of legacy PSS. The SSS sequence can be reused for eSSS.But ePSS as well as eSSS on CRS REs needs puncturing in frequencydomain. For ePSS detection, the MTC UEs may first de-scramble the covercodes for 3^(rd) and 4^(th) symbol group and combine the ePSS signals.

To combine the PBCH symbol with same symbol index in the 2-time PBCHrepetitions respectively (symbol-level combining) can cancel theinterference of the overlapped additional ePSS in 3^(rd) and 4^(th)symbol groups. Similar procedure as eSSS combining in the 1^(st) and2^(nd) symbol group. Note that the ePSS repetition and eSSS repetitioncan also be applied separately. For example, only the eSSS in 1^(st),2^(nd) symbol group multiplexed with {+1, −1} OCC but no additional ePSSrepetition on in 3^(rd) and 4^(th) symbol groups. For another example,only the ePSS in 3^(rd) and 4^(th) symbol group multiplexed with {+1,−1} OCC but no additional eSSS repetition on in 1st 2nd symbol groups.

In another sub-embodiment, ePSS in 1^(st), 2^(nd), 3^(rd) and 4^(th)symbol groups multiplexed with cover code, such as {+1, −1, +1, −1} OCC,is repeated, respectively. ePSS sequence length can be symbol-level withsimilar length as that of legacy PSS. A special case is to use theZadoff-Chu (ZC) sequence with length of 63 and root of 38, which isconjugate of ZC sequence PSS with root of 25. Or the ePSS is a longersequence with longer length around 2˜4 times that of legacy PSS. ButePSS on CRS REs needs puncturing in frequency domain.

To combine the PBCH symbol with same symbol index in the 4-time PBCHrepetitions respectively (symbol-level combining) can cancel theinterference of the overlapped additional ePSS symbol due to theorthogonality of cover codes. For ePSS detection, the MTC UEs may firstde-scramble the cover codes for each symbol group and combine the ePSSsignals. The PBCH signals are orthogonal to the ePSS signals.

In another sub-embodiment, repeat eSSS in 1^(st), 2^(nd), 3^(rd) and4^(th) symbol groups multiplexed with cover code, such as {+1, −1, +1,−1} OCC, is repeated, respectively. SSS can be simply reused for eSSS.But eSSS on CRS REs needs puncturing in frequency domain. To combine thePBCH symbol with same symbol index in the 4-time PBCH repetitionsrespectively (symbol-level combining) can cancel the interference of theoverlapped additional eSSS symbol due to the orthogonality of covercodes. For eSSS detection, the MTC UEs may first de-scramble the covercodes for each symbol group and combine the eSSS signals. The PBCHsignals are orthogonal to the eSSS signals.

Note that the similar concept can be extended for FDD frame structurewith extended CP (ECP). Also note that the other orthogonal cover codesare not precoded, such as the binary cover codes in the Hadamard matrix,or the complex cover codes in the P-matrix.

In some embodiments of component VI, a transmission and reception ofsynchronization signals for TDD is considered.

FIG. 19A illustrates yet another example transmission of an LC-MIB1900according to embodiments of the present disclosure. The embodiment ofthe transmission of an LC-MIB1900 illustrated in FIG. 19A is forillustration only. FIG. 19A does not limit the scope of this disclosure.

FIG. 19B illustrates yet another example transmission of an LC-MIB 1930according to embodiments of the present disclosure. The embodiment ofthe transmission of an LC-MIB 1930 illustrated in FIG. 19B is forillustration only. FIG. 19B does not limit the scope of this disclosure.

FIGS. 19A and 19B illustrate a transmission of an LC-MIB withrepetitions continuously in SF#0 and intermittently in SF#5 in a TDDsystem with a frame structure using normal CP. The MIB repetitions forLC-MIB with 1st, 2^(nd), 3^(rd), 4 and 5^(th) PBCH repeated symbols arealso shown in FIGS. 19A and 19B. But only the 1^(st), 3^(rd) and 4^(th)PBCH repetitions include the 2^(nd) and 3^(rd) PBCH symbols. The SF#0(subframe#0) includes the 1^(st) PBCH repetition and the SF#5 includesthe 3^(rd) PBCH repetition the 4^(th) PBCH repetition. Among the 4symbols in each PBCH repetition, the 0^(th) PBCH symbol and 1^(st) PBCHsymbol in each PBCH repetition including the CRS REs cannot beoverlapped with additional signals, which may be used for legacy MTC UEsas well as other non-MTC UEs for cell-specific channel estimation andRRM measurement. The remaining 2^(nd) PBCH symbol and 3^(rd) PBCH symbolin a PBCH repetition can be used to transmit additional sync signals,such as enhanced PSS and/or enhanced SSS (ePSS and/or eSSS).

The 2^(nd) PBCH symbol and 3^(rd) PBCH symbol in each PBCH repetitionwith similar channel variation are defined as a symbol group. There are2 symbol groups illustrated in FIGS. 19A and 19B. The two symbols inother groups are adjacent symbols. Each symbol group may be used to sendrepeated ePSS/eSSS and the symbol groups are group-multiplexed withorthogonal cover codes (OCC), such as {+1, −1}. The symbol grouplocations can neither overlap with CRS nor overlapped with PDCCH. Thesymbol group locations are not overlapped with the legacy PSS/SSS/PBCHto avoid any impact on the non-MTC UEs.

For example, 1^(st) symbol group with the slot and symbol numbertriplets (i, n′_(s), l′) with i=0 as (10, 5) and (10, 6); 2^(nd) symbolgroup with the slot and symbol number triplets (i, n′_(s), l′) with i=0as (11, 2) and (11, 3); One embodiment is to repeat ePSS in 1^(st) and2^(nd) symbol groups multiplexed with {+1, −1} OCC, respectively. ePSSsequence can be same as legacy PSS sequence. In one example, a longersequence for ePSS with 2 times that of legacy PSS to achieve bettercorrelation characteristics is considered. The longer sequence is mappedinto two symbols within a symbol group. To combine the 2^(nd) PBCHsymbol and 3^(rd) PBCH symbol in the 2-time PBCH repetitionsrespectively (symbol-level combining) can cancel the interference of theoverlapped additional ePSS symbol due to the OCC. For ePSS detection,the MTC UEs may first de-scramble the OCC for each symbol group andcombine the ePSS signals. The PBCH signals are orthogonal to the eSSSsignals.

In another embodiment, eSSS in 1^(st) and 2^(nd) symbol groupsmultiplexed with {+1, −1} OCC, is repeated, respectively. eSSS sequencecan be same as legacy SSS sequence. Another example is to a longersequence for eSSS with 2 times that of legacy SSS to achieve bettercorrelation characteristics. The longer sequence is mapped into twosymbols within a symbol group. To combine the 2^(nd) PBCH symbol and3^(rd) PBCH symbol in the 2-time PBCH repetitions respectively(symbol-level combining) can cancel the interference of the overlappedadditional eSSS symbol due to the OCC. For eSSS detection, the MTC UEsmay first de-scramble the OCC for each symbol group and combine the eSSSsignals. The PBCH signals are orthogonal to the eSSS signals.

In another embodiment, ePSS in the 1^(st) symbol of 1^(st) and 2^(nd)symbol groups multiplexed with {+1, −1} OCC, is repeated, respectively.ePSS sequence can be same as legacy PSS sequence. And repeat eSSS in the2^(nd) symbol of 1^(st) and 2^(nd) symbol groups multiplexed with {+1,−1} OCC, respectively. ePSS sequence can be same as legacy PSS sequence.To combine the 2^(nd) PBCH symbol in the 2-time PBCH repetitions(symbol-level combining) can cancel the interference of the overlappedadditional ePSS symbol due to the OCC. For ePSS detection, the MTC UEsmay first de-scramble the OCC for each symbol group and combine the ePSSsignals. The PBCH signals are orthogonal to the ePSS signals.

To combine the 3^(rd) PBCH symbol in the 2-time PBCH repetitions(symbol-level combining) can cancel the interference of the overlappedadditional eSSS symbol due to the OCC. For eSSS detection, the MTC UEsmay first de-scramble the OCC for each symbol group and combine the eSSSsignals. The PBCH signals are orthogonal to the eSSS signals. The ePSSand eSSS symbol can be shifted within each symbol group but all thesymbol groups has same order of ePSS and eSSS. Note that the similarconcept can be extended for TDD frame structure with extended CP (ECP).

FIG. 19C illustrates yet another example transmission of an LC-MIB 1950according to embodiments of the present disclosure. The embodiment ofthe transmission of an LC-MIB 1950 illustrated in FIG. 19C is forillustration only. FIG. 19C does not limit the scope of this disclosure.

FIG. 19D illustrates yet another example transmission of an LC-MIB 1970according to embodiments of the present disclosure. The embodiment ofthe transmission of an LC-MIB 1970 illustrated in FIG. 19D is forillustration only. FIG. 19D does not limit the scope of this disclosure.

FIGS. 19C and 19D illustrate a transmission of an LC-MIB withrepetitions continuously in SF#0 and intermittently in SF#5 in a TDDsystem with a frame structure using normal CP. The MIB repetitions forLC-MIB with 1^(st), 2^(nd), 3^(rd), 4^(th) and 5^(th) PBCH repeatedsymbols are also shown in FIGS. 19C and 19D. The 1 and 4^(th) PBCHrepetitions are used to carry ePSS/eSSS transmission. The SF#0(subframe#0) includes the 1^(st) and 2^(nd) PBCH repetitions and theSF#5 includes the 3^(rd), 4^(th) and 5^(th) PBCH repetitions. Among the4 symbols in each PBCH repetition, the CRS or CRS copy REs in the 0^(th)PBCH symbol and 1^(st) PBCH symbol per PBCH repetition cannot beoverlapped with additional signals, which may be used for legacy MTC UEsas well as other non-MTC UEs for cell-specific channel estimation andRRM measurement.

The corresponding REs in the 0^(th) and 1^(st) symbol per groupoverlapping with legacy. CRS REs may be punctured to avoid the impact onCRS reception at the price of the correlation performance of additionalsignals, such as ePSS and/or eSSS. The symbols in each PBCH repetitionwith similar channel variation are defined as a symbol group. There are4 symbol groups illustrated in FIGS. 19C and 19D. Each symbol group maybe used to send repeated ePSS/eSSS and the symbol groups aregroup-multiplexed with orthogonal cover codes (OCC), such as {+1, −1,+1, −1}. The symbol group locations can neither be overlapped withPDCCH, nor overlapped with the legacy PSS/SSS/PBCH to avoid any impacton the non-MTC UEs.

For example, 1^(st) symbol group with the slot and symbol numbertriplets (i, n′_(s), l′) with i=0 as (0, 3), (0, 4); 2^(nd) symbol groupwith the slot and symbol number triplets (i, n′_(s), l′) with i=0 as (1,4) and (1, 5); and 3^(rd) symbol group with the slot and symbol numbertriplets (i, n′_(s), l′) with i=0 as (10, 3) and (10, 4), (10, 5) and(10, 6); and 4^(th) symbol group with the slot and symbol numbertriplets (i, n′_(s), l′) with i=0 as (11, 0) and (11, 1), (11, 2) and(11, 3).

In one sub-embodiment, ePSS in the 2^(nd) and 3^(rd) symbols of 3^(rd)and 4^(th) symbol groups multiplexed with cover codes, such as {+1, −1}OCC, is repeated, respectively. The ePSS location with the frame offset,slot and symbol number triplets (i, n′_(s), l′) are (10, 5), (10, 6),(11, 2) and (11, 3). To let UE differentiate ePSS and legacy PSS, a newsequence is designed for ePSS. The ePSS sequence length can be same asthat of legacy PSS sequence.

A special case is to use the Zadoff-Chu (ZC) sequence with length of 63and root of 38, which is conjugate of ZC sequence PSS with root of 25.Since ePSS on the symbols without CRS does not need puncturing infrequency domain, the time-domain sequence correlation with the ZCsequence conjugate with that of PSS is simple from implementation pointof view. Or the ePSS is a longer sequence around 2 times that of legacyPSS. To combine the 2^(nd) and 3^(rd) PBCH symbols in the 2-time PBCHrepetitions (symbol-level combining) can cancel the interference of theoverlapped additional ePSS symbol due to the orthogonality of covercodes. For ePSS detection, the MTC UEs may firstly de-scramble the OCCfor each symbol group and combine the ePSS signals.

The PBCH signals are orthogonal to the ePSS signals. In addition to ePSSrepetition, the eSSS is repeated in the 0^(th) and 1^(st) symbols of1^(st), 2^(nd), 3^(rd) and 4^(th) symbol groups multiplexed with {+1,−1, +1, −1} OCC, respectively. The eSSS location with the frame offset,slot and symbol number triplets (i, n′_(s), l′) are (0, 3), (0, 4), (1,4), (1, 5), (10, 3), (10, 4), (11, 0) and (11, 1). The SSS sequence canbe reused for eSSS. But eSSS on CRS REs needs puncturing in frequencydomain. To combine the 0^(th) and 1^(st) PBCH symbol in the 4-time PBCHrepetitions (symbol-level combining) can cancel the interference of theoverlapped additional eSSS symbol due to the orthogonality of covercodes. For eSSS detection, the MTC UEs may first de-scramble the covercodes for each symbol group and combine the eSSS signals. The PBCHsignals are orthogonal to the eSSS signals.

In another sub-embodiment, ePSS in the 0^(th) and 1^(st) symbols of1^(st), 2^(nd), 3^(rd) and 4^(th) symbol groups multiplexed with covercodes, such as {+1, −1, +1, −1} OCC, is repeated, respectively. The ePSSlocation with the frame offset, slot and symbol number triplets (i,n′_(s), l′) are (0, 3), (0, 4), (1, 4), (1, 5), (10, 3), (10, 4), (11,0), and (11, 1). The ePSS can be a short sequence with similar length oflegacy PSS length. Or the ePSS is a longer sequence around 2 times thatof legacy PSS. But ePSS on CRS REs needs puncturing in frequency domain.To combine the 0^(th) and 1^(st) PBCH symbols in the 4-time PBCHrepetitions (symbol-level combining) can cancel the interference of theoverlapped additional ePSS symbol due to the orthogonality of covercodes.

For ePSS detection, the MTC UEs may firstly de-scramble the OCC for eachsymbol group and combine the ePSS signals. The PBCH signals areorthogonal to the ePSS signals. In addition to ePSS repetition, the eSSSis repeated in the 2^(nd) and 3^(rd) symbols of 3^(rd) and 4^(th) symbolgroups multiplexed with {+1, −1, +1, −1} OCC, respectively. The eSSSlocation with the frame offset, slot and symbol number triplets (i,n′_(s), l′) are (10, 5), (10, 6), (11, 2) and (11, 3). The SSS sequencecan be reused for eSSS. To combine the 2^(nd) and 3^(rd) PBCH symbol inthe 2-time PBCH repetitions (symbol-level combining) can cancel theinterference of the overlapped additional eSSS symbol due to theorthogonality of cover codes. For eSSS detection, the MTC UEs may firstde-scramble the cover codes for each symbol group and combine the eSSSsignals. The PBCH signals are orthogonal to the eSSS signals.

In another sub-embodiment, ePSS in 1^(st), 2^(nd) symbol groupmultiplexed with cover code, such as {+1, −1} OCC, is repeated,respectively. And repeat eSSS in 3^(rd) and 4^(th) symbol groupsmultiplexed with {+1, −1}. The ePSS location with the frame offset, slotand symbol number triplets (i, n′_(s), l′) are (0, 3), (0, 4), (1, 4)and (1, 5). The eSSS location with the frame offset, slot and symbolnumber triplets (i, n′_(s), l′) are (10, 3) and (10, 4), (10, 5), (10,6), (11, 0) and (11, 1), (11, 2) and (11, 3). The ePSS sequence can besymbol-level with similar length of legacy PSS sequence. Or the ePSS isa longer sequence with longer length around 2 times that of legacy PSS.

The SSS sequence can be reused for eSSS. But ePSS as well as eSSS on CRSREs needs puncturing in frequency domain. For ePSS detection, the MTCUEs may first de-scramble the cover codes for 1^(st) and 2^(nd) symbolgroup and combine the ePSS signals. To combine the PBCH symbol with samesymbol index in the 2-time PBCH repetitions respectively (symbol-levelcombining) can cancel the interference of the overlapped additional ePSSin 1^(st) and 2^(nd) symbol groups. Similar procedure as eSSS combiningin the 3^(rd) and 4^(th) symbol group.

Note that the ePSS repetition and eSSS repetition can also be appliedseparately. For example, only the ePSS in 1^(st), 2^(nd) symbol groupmultiplexed with {+1, −1} OCC but no additional eSSS repetition on in3^(rd) and 4^(th) symbol groups. For another example, only the eSSS in3^(rd) and 4^(th) symbol group multiplexed with {+1, −1} OCC but noadditional ePSS repetition on in 1^(st), 2^(nd) symbol groups.

In another sub-embodiment, eSSS in 1^(st), 2^(nd) symbol groupmultiplexed with cover code, such as {+1, −1} OCC, is repeated,respectively. And repeat ePSS in 3^(rd) and 4^(th) symbol groupsmultiplexed with {+1, −1}. The eSSS location with the frame offset, slotand symbol number triplets (i, n′_(s), l′) are (0, 3), (0, 4), (1, 4)and (1, 5). The ePSS location with the frame offset, slot and symbolnumber triplets (i, n′_(s), l′) are (10, 3) and (10, 4), (10, 5), (10,6), (11, 0) and (11, 1), (11, 2) and (11, 3). The ePSS sequence can besymbol-level with similar length of legacy PSS sequence. Or the ePSS isa longer sequence with longer length around 2 or 4 times that of legacyPSS.

The SSS sequence can be reused for eSSS. But ePSS as well as eSSS on CRSREs needs puncturing in frequency domain. For ePSS detection, the MTCUEs may first de-scramble the cover codes for 3^(rd) and 4^(th) symbolgroup and combine the ePSS signals. To combine the PBCH symbol with samesymbol index in the 2-time PBCH repetitions respectively (symbol-levelcombining) can cancel the interference of the overlapped additional ePSSin 3^(rd) and 4^(th) symbol groups. Similar procedure as eSSS combiningin the 1^(st) and 2^(nd) symbol group. Note that the ePSS repetition andeSSS repetition can also be applied separately.

For example, only the eSSS in 1^(st), 2^(nd) symbol group multiplexedwith {+1, −1} OCC but no additional ePSS repetition on in 3^(rd) and4^(th) symbol groups. For another example, only the ePSS in 3^(rd) and4^(th) symbol group multiplexed with {+1, −1} OCC but no additional eSSSrepetition on in 1^(st), 2^(nd) symbol groups.

In another sub-embodiment, ePSS in 1^(st), 2^(nd), 3^(rd) and 4^(th)symbol groups multiplexed with cover code, such as {+1, −1, +1, −1} OCC,is repeated, respectively. ePSS sequence length can be symbol-level withsimilar length as that of legacy PSS. A special case is to use theZadoff-Chu (ZC) sequence with length of 63 and root of 38, which isconjugate of ZC sequence PSS with root of 25. Or the ePSS is a longersequence with longer length around 2 times that of legacy PSS. But ePSSon CRS REs needs puncturing in frequency domain.

To combine the PBCH symbol with same symbol index in the 4-time PBCHrepetitions respectively (symbol-level combining) can cancel theinterference of the overlapped additional ePSS symbol due to theorthogonality of cover codes. For ePSS detection, the MTC UEs may firstde-scramble the cover codes for each symbol group and combine the ePSSsignals. The PBCH signals are orthogonal to the ePSS signals.

In another sub-embodiment, eSSS in 1^(st), 2^(nd), 3^(rd) and 4^(th)symbol groups multiplexed with cover code, such as {+1, −1, +1, −1} OCC,is repeated, respectively. SSS can be simply reused for eSSS. But eSSSon CRS REs needs puncturing in frequency domain. To combine the PBCHsymbol with same symbol index in the 4-time PBCH repetitionsrespectively (symbol-level combining) can cancel the interference of theoverlapped additional eSSS symbol due to the orthogonality of covercodes. For eSSS detection, the MTC UEs may first de-scramble the covercodes for each symbol group and combine the eSSS signals. The PBCHsignals are orthogonal to the eSSS signals.

Note that the similar concept can be extended for FDD frame structurewith extended CP (ECP). Also note that the other orthogonal cover codesare not precoded, such as the binary cover codes in the Hadamard matrix,or the complex cover codes in the P-matrix.

FIG. 20A illustrates an example a transmission of enhancedsynchronization signals 2000 according to embodiments of the presentdisclosure. The embodiment of the transmission of enhancedsynchronization signals 2000 illustrated in FIG. 20A is for illustrationonly. FIG. 20A does not limit the scope of this disclosure.

FIG. 20B illustrates another example a transmission of enhancedsynchronization signals 2030 according to embodiments of the presentdisclosure. The embodiment of the transmission of enhancedsynchronization signals 2030 illustrated in FIG. 20B is for illustrationonly. FIG. 20B does not limit the scope of this disclosure.

FIGS. 20A and 20B illustrate a transmission of enhanced synchronizationsignals in the special subframes with DL/UL configuration in SF#1 andintermittently in SF#6 in a TDD system with a frame structure usingnormal CP. In SF#1 and #6, the 12 DL symbols are used to enable theePSS/eSSS transmission. In slot#3, the 1-symbol GP in slot and symbolnumber triplets (i, n′_(s), l′) with 1=0 of (3, 5) and I-symbol ULsymbol in slot and symbol number triplets (i, n′_(s), l′) with i=0 of(3, 6) are configured respectively. In slot#13, the 1-symbol GP in slotand symbol number triplets (i, n′_(s), l′) with i=0 of (13, 5) and1-symbol UL symbol in slot and symbol number triplets (i, n′_(s), l′)with i=0 of (13, 6) are configured respectively.

These symbols in SF#1 and SF#6 are not overlapped with the MIBrepetitions for LC-MIB with 1^(st), 2^(nd), 3^(rd), 4^(th) and 5^(th)PBCH repeated symbols in SF#0 and SF#5 are also shown in FIGS. 20A and20B. Among the 12 DL symbols in SF#1 and Sf#6, the symbols including thelegacy PSS and the CRS REs cannot be overlapped with additional signals,which may be used for legacy MTC UEs as well as other non-MTC UEs forinitial synchronization, cell searching, cell-specific channelestimation and RRM measurement, The remaining symbols for PDSCH can beused to transmit additional sync signals, such as enhanced PSS and/orenhanced SSS (ePSS and/or eSSS).

The adjacent symbols in each PBCH repetition with similar channelvariation are defined as a symbol group. There are 4 symbol groupsillustrated in FIGS. 20A and 20B. Each symbol group may be used to sendrepeated ePSS/eSSS. The symbol group locations can neither overlap withCRS nor overlapped with PDCCH. The symbol group locations are notoverlapped with the legacy PSS/SSS/PBCH to avoid any impact on thenon-MTC UEs.

Note that if the symbol groups are group-multiplexed with orthogonalcover codes (OCC), such as {+1, −1}, it is possible to consider thePDSCH transmission in the overlapped symbol groups for ePSS/SSSrepetition to further increase the spectral efficiency in SF#1 and SF#6.

For example, 1^(st) symbol group with the slot and symbol numbertriplets (i, n′_(s), l′) with i=0 as (2, 5) and (2, 6); 2^(nd) symbolgroup with the slot and symbol number triplets (i, n′_(s), l′) with i=0as (3, 2) and (3, 3); 3^(rd) symbol group with the slot and symbolnumber triplets (i, n′_(s), l′) with i=0 as (12, 5) and (12, 6); and4^(th) symbol group with the slot and symbol number triplets (i, n′_(s),l′) with i=0 as (13, 2) and (13, 3).

In one sub-embodiment, ePSS in 1^(st), 2^(nd), 3^(rd) and 4^(th) symbolgroups, is repeated respectively. ePSS sequence can be same as legacyPSS sequence. Another example is to a longer sequence for ePSS with 2times that of legacy PSS to achieve better correlation characteristics.The longer sequence is mapped into two symbols within a symbol group.For ePSS detection, the MTC UEs can combine the ePSS correlation signalswithin the same slot and/or in different slots.

In another sub-embodiment, repeat eSSS in 1^(st), 2^(nd), 3^(rd) and4^(th) symbol groups, is repeated, respectively. eSSS sequence can besame as legacy PSS sequence. Another example is to a longer sequence foreSSS with 2 times that of legacy PSS to achieve better correlationcharacteristics. The longer sequence is mapped into two symbols within asymbol group. For eSSS detection, the MTC UEs can combine the eSSScorrelation signals within the same slot and/or in different slots.

In another sub-embodiment, ePSS in 1^(st), 2^(nd) symbol group isrepeated and eSSS in 3^(rd) and 4^(th) symbol groups is repeated. TheePSS sequence can be same as legacy PSS sequence or a longer sequencefor ePSS with 2 times that of legacy PSS to achieve better correlationcharacteristics. Similarly the eSSS sequence can be same as legacy SSSsequence or a longer sequence for eSSS with 2 times that of legacy SSSto achieve better correlation characteristics. For ePSS detection, theMTC UEs can combine the ePSS correlation signals.

For eSSS detection, the MTC UEs combine the eSSS correlation signals.Note that the ePSS repetition and eSSS repetition can be appliedseparately. For example, only the ePSS in 1^(st), symbol group but noadditional eSSS repetition on in 3^(rd) and 4^(th) symbol groups. Foranother example, only the eSSS in 3^(rd) and 4^(th) symbol group but noadditional ePSS repetition on in 1^(st), 2^(nd) symbol groups.

In another sub-embodiment, eSSS in 1^(st), 2^(nd) symbol group isrepeated and ePSS in 3^(rd) and 4^(th) symbol groups is repeated. TheeSSS sequence can be same as legacy SSS sequence or a longer sequencefor eSSS with 2 times that of legacy SSS to achieve better correlationcharacteristics. Similarly the ePSS sequence can be same as legacy PSSsequence or a longer sequence for ePSS with 2 times that of legacy PSSto achieve better correlation characteristics. For eSSS detection, theMTC UEs can combine the eSSS correlation signals.

For ePSS detection, the MTC UEs combine the ePSS correlation signals.Note that the eSSS repetition and ePSS repetition can be appliedseparately. For example, only the eSSS in 1^(st), 2^(nd) symbol groupbut no additional ePSS repetition on in 3^(rd) and 4^(th) symbol groups.For another example, only the ePSS in 3^(rd) and 4^(th) symbol group butno additional eSSS repetition on in 1^(st), 2^(nd) symbol groups.

In another embodiment, ePSS in the 1^(st) symbol of 1^(st), 2^(nd),3^(rd) and 4^(th) symbol groups, is repeated, respectively. ePSSsequence can be same as legacy PSS sequence. And repeat eSSS in the2^(nd) symbol of 1^(st), 2^(nd), 3^(rd) and 4^(th) symbol groups,respectively. ePSS sequence can be same as legacy PSS sequence. For ePSSdetection, the MTC combine the ePSS correlation signals in the ePSSsymbols. For eSSS detection, the MTC combine the eSSS correlationsignals in the eSSS symbols. The ePSS and eSSS symbol can be shiftedwithin each symbol group but all the symbol groups has same order ofePSS and eSSS.

In another embodiment, ePSS next to the legacy PSS in SF#1 and SF#6, isrepeated, respectively. The special symbol is illustrated as in FIGS.20A and 20B.

For example, 1^(st) special symbol with the slot and symbol numbertriplets (i, n′_(s), l′) with i=0 as (2, 3); and 2^(nd) special symbolwith the slot and symbol number triplets (i, n′_(s), l′) with i=0 as(12, 3).

In one embodiment, ePSS in 1^(st), 2^(nd) special symbols, is sent,respectively. ePSS sequence can be same as legacy PSS sequence. For ePSSdetection, the MTC UEs can combine the ePSS correlation signals withinthe same slot and/or in different slots.

In another embodiment, eSSS in 1^(st), 2^(nd) special symbols, is sent,respectively. eSSS sequence can be same as legacy SSS sequence. For eSSSdetection, the MTC UEs can combine the eSSS correlation signals withinthe same slot and/or in different slots.

Note that the special symbols for ePSS/eSSS can be applied together withthe other symbol groups in FIGS. 20A and 20B or independently used.

Note that the similar concept can be extended for TDD frame structurewith extended CP (ECP).

FIG. 20C illustrates yet another example a transmission of enhancedsynchronization signals 2050 according to embodiments of the presentdisclosure. The embodiment of the transmission of enhancedsynchronization signals 2050 illustrated in FIG. 20C is for illustrationonly. FIG. 20C does not limit the scope of this disclosure.

FIG. 20D illustrates yet another example a transmission of enhancedsynchronization signals 2070 according to embodiments of the presentdisclosure. The embodiment of the transmission of enhancedsynchronization signals 2070 illustrated in FIG. 20D is for illustrationonly. FIG. 20D does not limit the scope of this disclosure.

FIGS. 20C and 20D illustrate a transmission of enhanced synchronizationsignals in the special subframes with DL/UL configuration in SF#1 andintermittently in SF#6 in a TDD system with a frame structure usingnormal CP. In SF#1 and #6, the 18 DL symbols are used to enable theePSS/eSSS transmission. In slot#3, the 1-symbol GP in slot and symbolnumber triplets (i, n′_(s), l′) with i=0 of (3, 5) and 1-symbol ULsymbol in slot and symbol number triplets (i, n′_(s), l′) with i=0 of(3, 6) are configured respectively. In slot#13, the 1-symbol GP in slotand symbol number triplets (i, n′_(s), l′) with i=0 of (13, 5) and1-symbol UL symbol in slot and symbol number triplets (i, n′_(s), l′)with i=0 of (13, 6) are configured respectively.

These symbols in SF#1 and SF#6 are not overlapped with the MIBrepetitions for LC-MIB with 1st, 2nd, 3rd, 4th and 5th PBCH repeatedsymbols in SF#0 and SF#5 are also shown in FIGS. 20C and 20D. Among the18 DL symbols in SF#1 and Sf#6, the PSS symbols and the CRS REs cannotbe overlapped with additional signals, which may be used for legacy MTCUEs as well as other non-MTC UEs for initial synchronization, cellsearching, cell-specific channel estimation and RRM measurement. Theremaining REs for PDSCH can be used to transmit additional sync signals,such as enhanced PSS and/or enhanced SSS (ePSS and/or eSSS). The symbolswith CRS and the symbols without CRS can be divided into differentsymbol groups. Each symbol group may be used to send repeated ePSS/eSSS.The symbol group locations cannot be overlapped with PDCCH, neitheroverlapped with the legacy PSS/SSS/PBCH to avoid any impact on thenon-MTC UEs.

For example, 1^(st) symbol group with the slot and symbol numbertriplets (i, n′_(s), l′) with i=0 as (2, 3), (2, 5), (2, 6), (3, 2), (3,3); 2^(nd) symbol group with the slot and symbol number triplets (i,n′_(s), l′) with i=0 as (12, 3), (12, 5), (12, 6), (13, 2), (13, 3);3^(rd) symbol group with the slot and symbol number triplets (i, n′_(s),l′) with i=0 as (2, 4), (3, 0), (3, 1) and (3, 4); and 4^(th) symbolgroup with the slot and symbol number triplets (i, n′_(s), l′) with i=0as (12, 4), (13, 0), (13, 1) and (13, 4).

In one sub-embodiment, ePSS in 1^(st), 2^(nd) symbol group and repeateSSS in 3^(rd) and 4^(th) symbol groups is repeated. The ePSS sequencecan be same as legacy PSS sequence or a longer sequence for ePSS with 5times that of legacy PSS to achieve better correlation characteristics.A special case is to use the Zadoff-Chu (ZC) sequence with length of 63and root of 38, which is conjugate of ZC sequence PSS with root of 25.Since ePSS on the symbols without CRS does not need puncturing infrequency domain, the time-domain sequence correlation with the ZCsequence conjugate with that of PSS is simple from implementation pointof view.

The eSSS sequence can be same as legacy SSS sequence or a longersequence for eSSS with 4 times that of legacy SSS to achieve bettercorrelation characteristics. But eSSS on CRS REs needs puncturing infrequency domain. For ePSS detection, the MTC UEs can combine the ePSScorrelation signals. For eSSS detection, the MTC UEs combine the eSSScorrelation signals. Note that the ePSS repetition and eSSS repetitioncan be applied separately. For example, only the ePSS in 1^(st), 2^(nd)symbol group but no additional eSSS repetition on in 3^(rd) and 4^(th)symbol groups. For another example, only the eSSS in 3^(rd) and 4^(th)symbol group but no additional ePSS repetition on in 1^(st), 2^(nd)symbol groups.

In another sub-embodiment, eSSS in 1^(st), 2^(nd) symbol group andrepeat ePSS in 3^(rd) and 4^(th) symbol groups is repeated. The ePSSsequence can be same as legacy PSS sequence or a longer sequence forePSS with 4 times that of legacy PSS to achieve better correlationcharacteristics. The eSSS sequence can be same as legacy SSS sequence ora longer sequence for eSSS with 5 times that of legacy SSS to achievebetter correlation characteristics. A special case is to use theZadoff-Chu (ZC) sequence with length of 63 and root of 38, which isconjugate of ZC sequence PSS with root of 25. But ePSS on CRS REs needspuncturing in frequency domain.

For ePSS detection, the MTC UEs can combine the ePSS correlationsignals. For eSSS detection, the MTC UEs combine the eSSS correlationsignals. Note that the ePSS repetition and eSSS repetition can beapplied separately. For example, only the eSSS in 1^(st), 2^(nd) symbolgroup but no additional ePSS repetition on in 3^(rd) and 4^(th) symbolgroups. For another example, only the ePSS in 3^(rd) and 4^(th) symbolgroup but no additional eSSS repetition on in 1^(st), 2^(nd) symbolgroups.

In another sub-embodiment, ePSS in 1^(st), 2^(nd), 3^(rd) and 4^(th)symbol groups is repeated. The ePSS sequence can be same as legacy PSSsequence or a longer sequence for ePSS with 5 times that of legacy PSSto achieve better correlation characteristics.

In another sub-embodiment, eSSS in 1^(st), 2^(nd), 3^(rd) and 4^(th)symbol groups is repeated. The eSSS sequence can be same as legacy SSSsequence or a longer sequence for eSSS with 5 times that of legacy SSSto achieve better correlation characteristics.

Note that the partial symbols per symbol group can be used for ePSSand/or eSSS transmission.

Note that the similar concept can be extended for TDD frame structurewith extended CP (ECP).

An MIB for LC-UEs is referred to as LC-MIB as it can utilize spare bitsof an existing MIB to provide scheduling information for an LC-SIB-1transmission. As an LC-UE is not aware of the UL/DL configuration incase of a TDD system or, in general, of ABS or MBSFN SFs when the LC-UEneeds to detect the LC-MIB, an LC-MIB transmission needs to occur onlyin SFs that are guaranteed to be DL SFs regardless of the UL/DLconfiguration or of the presence of ABS or MBSFN SFs. For LC-MIBtransmission, an LC-UE can assume that a conventional DL control regionspans 3 SF symbols. This represents a maximum number of SF symbols forthe conventional DL control region for all DL system BWs except forsmall DL system BWs (see also REF 1). However, for small DL system BWs,as only limited DL scheduling (if any) can exist in SFs with LC-MIBtransmission, 3 SF symbols are adequate for the conventional DL controlregion without imposing adverse scheduling restrictions.

FIGS. 18A and 18B illustrate a transmission of an LC-MIB withrepetitions continuously in SF#0 and intermittently in SF#5 in a FDDsystem with a frame structure using normal CP. The MIB repetitions forLC-MIB with 1^(st), 2^(nd), 3^(rd) and 4^(th) PBCH repeated symbols arealso shown in FIGS. 18A and 18B. The SF#9 (subframe#9) includes the1^(st) and 2^(nd) PBCH repetition and part of 3^(rd) PBH repetition andthe SF#0 includes the remaining of 3^(rd) PBCH and the 4^(th) PBCHrepetition. Among the 4 symbols in each PBCH repetition, the 0^(th) PBCHsymbol and 1^(st) PBCH symbol in each PBCH repetition include the CRSREs, which may be used for legacy MTC UEs as well as other non-MTC UEsfor cell-specific channel estimation and RRM measurement, which cannotbe overlapped with additional signals.

FIGS. 19A and 19B illustrate a transmission of an LC-MIB withrepetitions continuously in SF#0 and intermittently in SF#5 in a TDDsystem with a frame structure using normal CP. The MIB repetitions forLC-MIB with 1^(st), 2^(nd), 3^(rd), 4^(th) and 5^(th) PBCH repeatedsymbols are also shown in FIGS. 19A and 19B. But only the 1st 3^(rd) and4^(th) PBCH repetitions include the 2^(nd) and 3^(rd) PBCH symbols. TheSF#0 (subframe#0) includes the 1^(st) PBCH repetition and the SF#5includes the 3^(rd) PBCH repetition the 4^(th) PBCH repetition. Amongthe 4 symbols in each PBCH repetition, the 0^(th) PBCH symbol and 1^(st)PBCH symbol in each PBCH repetition include the CRS REs, which may beused for legacy MTC UEs as well as other non-MTC UEs for cell-specificchannel estimation and RRM measurement, which cannot be overlapped withadditional signals.

LC-UEs target 20 dB improved coverage using very low rate traffic withrelated latency requirement. The coverage for legacy LTE PSS/SSS needsto be improved 11.4 dB for FDD and 17.4 dB for TDD in order to achievean overall coverage enhancement target of 20 dB. For normal LTE, the SCHoperating point for an FDD system is at −7.8 dB. Additional 11.4 dB isneeded for coverage enhancement, resulting in the required operatingpoint of −19.2 dB.

Therefore, there is a need to enable additional transmission of PSSand/or SSS to improve the synchronization latency for LC-UEs.

There is another need to design sequences and mappings for PSS and/orSSS such that the detection complexity of LC-UEs is low.

There is another need to design sequences and mappings for PSS and/orSSS such that the synchronization performance of traditional UEs are notimpacted.

In some embodiments of component VII for sequence Design of ePSS, thefunctionality of PSS is to provide coarse time domain and frequencydomain synchronization, as well as part of the physical cell IDdetection. The PSS is constructed from a frequency-domain Zadoff-Chu(ZC) sequence of length 63, with the middle element truncated to avoidusing the d.c. subcarrier. 3 roots are selected for PSS to represent the3 physical layer identities within each group of cells (e.g. N_(ID)⁽²⁾). The PSS is transmitted in the central 6 Resource Blocks (RBs),invariant to the system bandwidth to enable the UE to synchronizewithout a priori information of the system bandwidth. More precisely,the sequence to generate PSS is given by

${d_{PSS}(n)} = \{ \begin{matrix}{e^{{- j}\frac{\pi \; {{un}{({n + 1})}}}{63}},} & {{n = 0},1,\ldots \mspace{14mu},30} \\{e^{{- j}\frac{\pi \; {u{({n + 1})}}{({n + 2})}}{63}},} & {{n = 31},\ldots \mspace{14mu},61}\end{matrix} $

where the ZC-sequence root index u is given by TABLE 4.

TABLE 4 ZC-sequence root index N_(ID) ⁽²⁾ u 0 25 1 29 2 34

In some embodiments, ePSS is only responsible for detection of timingand frequency offset, and does not carry cell ID information. In thisembodiment, ePSS is purely utilized for additional time and frequencydomain synchronization, and single sequence is utilized for generatingePSS. The single sequence to generate ePSS can be selected from one ofthe following options.

In one example of option 1, the sequence to generate ePSS is the same asone of the sequences to generate PSS. More precisely, the sequence togenerate ePSS is given by

${d_{ePSS}(n)} = \{ \begin{matrix}{e^{{- j}\frac{\pi \; {{vn}{({n + 1})}}}{63}},} & {{n = 0},1,\ldots \mspace{14mu},30} \\{e^{{- j}\frac{\pi \; {v{({n + 1})}}{({n + 2})}}{63}},} & {{n = 31},\ldots \mspace{14mu},61}\end{matrix} $

where v=25 or 29 or 34, and d_(ePSS) (n) is mapped in thefrequency-domain to the center 62 REs within the synchronizationtransmission bandwidth.

In one example of option 2, the sequence to generate ePSS is theconjugate sequence of the ZC-sequence to generate PSS with root indexu=25. More precisely, the sequence to generate ePSS is given by

${d_{ePSS}(n)} = \{ \begin{matrix}{e^{{- j}\frac{\pi \; {{vn}{({n + 1})}}}{63}},} & {{n = 0},1,\ldots \mspace{14mu},30} \\{e^{{- j}\frac{\pi \; {v{({n + 1})}}{({n + 2})}}{63}},} & {{n = 31},\ldots \mspace{14mu},61}\end{matrix} $

where v=38 (root index 38 is the conjugate of root index 25), andd_(ePSS) (n) is mapped in the frequency-domain to the center 62 REswithin the synchronization transmission bandwidth.

In one example of option 3, the sequence to generate ePSS is aZC-sequence having small correlation with existing sequences to generatePSS, and has good sequence performance like PAPR, RCM, and capabilityagainst CFO. More precisely, the sequence to generate ePSS is given by

${d_{ePSS}(n)} = \{ \begin{matrix}{e^{{- j}\frac{\pi \; {{vn}{({n + 1})}}}{63}},} & {{n = 0},1,\ldots \mspace{14mu},30} \\{e^{{- j}\frac{\pi \; {v{({n + 1})}}{({n + 2})}}{63}},} & {{n = 31},\ldots \mspace{14mu},61}\end{matrix} $

where v=9 or 12 or 21 or 30 or 33 or 42 or 51 or 54, and d_(ePSS)(n) ismapped in the frequency-domain to the center 62 REs within thesynchronization transmission bandwidth.

In some embodiments, ePSS is responsible for detection of timing andfrequency offset, as well as for detection of part of cell ID (e.g.N_(ID) ⁽²⁾). In this embodiment, the number of sequences to generateePSS is the same as the number of sequences to generate PSS (i.e., 3sequences corresponding to 3 cell ID hypotheses carried by PSS). Thesequence for generating ePSS can be selected from one of the followingoptions.

In one example of option 1, the three sequences to generate ePSS are thesame as the sequences to generate PSS. More precisely, the sequences togenerate ePSS are given by

${d_{ePSS}(n)} = \{ \begin{matrix}{e^{{- j}\frac{\pi \; {{vn}{({n + 1})}}}{63}},} & {{n = 0},1,\ldots \mspace{14mu},30} \\{e^{{- j}\frac{\pi \; {v{({n + 1})}}{({n + 2})}}{63}},} & {{n = 31},\ldots \mspace{14mu},61}\end{matrix} $

where v is given by TABLE 5, and d_(ePSS) (n) is mapped in thefrequency-domain to the center 62 REs within the synchronizationtransmission bandwidth.

TABLE 5 ePSS generation parameter N_(ID) ⁽²⁾ v 0 25 1 29 2 34

In one example of option 2, the three sequences to generate ePSS are theZC-sequences having small correlation with existing sequences togenerate PSS, and have good sequence performance like PAPR, RCM, andcapability against CFO. More precisely, the sequences to generate ePSSare given by

${d_{ePSS}(n)} = \{ \begin{matrix}{e^{{- j}\frac{\pi \; {{vn}{({n + 1})}}}{63}},} & {{n = 0},1,\ldots \mspace{14mu},30} \\{e^{{- j}\frac{\pi \; {v{({n + 1})}}{({n + 2})}}{63}},} & {{n = 31},\ldots \mspace{14mu},61}\end{matrix} $

where v is given by TABLE 6 (x can be 9 or 12 or 21 or 30 or 33 or 42 or51 or 54), and d_(ePSS)(n) is mapped in the frequency-domain to thecenter 62 REs within the synchronization transmission bandwidth.

TABLE 6 ePSS generation parameter N_(ID) ⁽²⁾ v 0 38 1 x 2 63 − x

In some embodiments of component VIII for sequence Design of eSSS inLTE, the functionality of SSS sequence is to detect the other part ofcell ID based on the coarse time-domain and frequency-domainsynchronization detection from PSS. CP size and duplexing modeinformation are also detected by SSS sequence and its relative locationwith PSS. The construction of SSS sequences are based on the maximumlength sequences (also known as M-sequences).

Each SSS sequence is constructed by interleaving two length-31 BPSKmodulated subsequences in frequency domain, where the two subsequencesare constructed from the same M-sequence using different cyclic shifts.The cyclic shift indices for both parts are functions of the physicalcell ID group. More precisely, the sequence to generate SSS is given bythe combination of two length-31 sequences differing between subframesaccording to

${d_{SSS}( {2n} )} = \{ {\begin{matrix}{{{s_{0}^{(m_{0})}(n)}{c_{0}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 0},1,2,3,4} \\{{{s_{1}^{(m_{1})}(n)}{c_{0}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 5},6,7,8,9}\end{matrix},{{d_{SSS}( {{2n} + 1} )} = \{ \begin{matrix}{{{s_{1}^{(m_{1})}(n)}{c_{1}(n)}{z_{1}^{(m_{0})}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 0},1,2,3,4} \\{{{s_{0}^{(m_{0})}(n)}{c_{1}(n)}{z_{1}^{(m_{1})}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 5},6,7,8,9}\end{matrix} }} $

where 0≤n≤30. The indices m₀ and m₁ are derived from the physical-layercell-identity group N_(ID) ⁽¹⁾ according to

${m_{0} = {m^{\prime}{mod}\; 31}},{m_{1} = {( {m_{0} + \lfloor \frac{m^{\prime}}{31} \rfloor + 1} ){mod}\; 31}},{m^{\prime} = {N_{ID}^{(1)} + {{q( {q + 1} )}/2}}},{q = \lfloor {( {N_{ID}^{(1)} + {{q^{\prime}( {q^{\prime} + 1} )}/2}} )/30} \rfloor},{g^{\prime} = {\lfloor {N_{ID}^{(1)}/30} \rfloor.}}$

The two sequences s₀ ^((m) ⁰ ⁾(n) and s₁ ^((m) ¹ ⁾(n) are defined as twodifferent cyclic shifts of the M-sequence {tilde over (s)}(n) accordingto s₀ ^((m) ⁰ ⁾(n)={tilde over (s)}((n+m₀) mod 31), s₁ ^((m) ¹⁾(n)={tilde over (s)}((n+m₁) mod 31) where {tilde over (s)}(i)=1−2x(i),0≤i≤30, is defined by x(ι+5)=(x(ι+2)+x(0) mod 2, 0≤ι≤25 with initialconditions x(0)=x(1)=x(2)=x(3)=0, and x(4)=1.

The two scrambling sequences c₀(n) and c₁(n) depend on N_(ID) ⁽²⁾ in PSSand are defined by two different cyclic shifts of the M-sequence {tildeover (c)}(n) according to c₀(n)={tilde over (c)}((n+N_(ID) ⁽²⁾) mod 31),c₁(n)={tilde over (c)}((n+N_(ID) ⁽²⁾+3) mod 31) where N_(ID) ^((2)∈{)0,1, 2} is the physical-layer identity within the physical-layer cellidentity group Ng) and c(i)=1−2x(i), 0≤i≤30, is defined byx(ι+5)=(x(ι+3)+x(0) mod 2, 0ι25 with initial conditionsx(0)=x(1)=x(2)=x(3)=0, and x(4)=1. The two scrambling sequences z₁ ^((m)⁰ ⁾(n) and z₁ ^((m) ¹ ⁾(n) defined by a cyclic shift of M-sequence{tilde over (z)}(n) according to z₀ ^((m) ⁰ ⁾(n)=2((n+(m₀ mod 8)) mod31), z₁ ^((m) ¹ ⁾(n)={tilde over (z)}((n+(m₁ mod 8)) mod 31) where{tilde over (z)}(i)=1−2x(i), 0≤i≤30, is defined byx(ι+5)=(x(ι+4)+x(ι+2)+x(ι+1)+x(ι) mod 2, 0≤ι≤25 with initial conditionsx(0)=x(1)=x(2)=x(3)=0, and x(4)=1.

In some embodiment, the sequence to generate eSSS is similar to thesequence to generate SSS (the associated subframe numbers differ fromSSS because the time-domain mapping of eSSS can be different, and notethat if eSSS is mapped to the same subframes as SSS, the sequence togenerate eSSS is the same as the one to generate SSS), where thesequence is also given by the combination of two length-31 sequences,and scrambled by N_(ID) ⁽²⁾. For example, the construction of sequenceto generate eSSS can be according to

${d_{eSSS}( {2n} )} = \{ {\begin{matrix}{{{s_{0}^{(m_{0})}(n)}{c_{0}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 8},9,0,1,2} \\{{{s_{1}^{(m_{1})}(n)}\; {c_{0}(n)}\mspace{11mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 3},4,5,6,7}\end{matrix},{{d_{eSSS}( {{2n} + 1} )} = \{ \begin{matrix}{{{s_{1}^{(m_{1})}(n)}{c_{1}(n)}{z_{1}^{(m_{0})}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 8},9,0,1,2} \\{{{s_{0}^{(m_{0})}(n)}{c_{1}(n)}{z_{1}^{(m_{1})}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 3},4,5,6,7}\end{matrix} }} $

where 0≤n≤30, and m₀, m₁, s₀ ^((m) ⁰ ⁾(n), s₁ ^((m) ¹ ⁾(n), c₀(n),c₁(n), z₁ ^((m) ⁰ ⁾(n), and z₁ ^((m) ¹ ⁾(n) are same as the ones ingenerating SSS. d_(eSSS)(n) is mapped in the frequency-domain to thecenter 62 REs within the synchronization transmission bandwidth.

In some embodiments, the sequence to generate eSSS is given by thecombination of two length-31 sequences, but not scrambled by N_(ID) ⁽²⁾.For example, the construction of sequence to generate eSSS can beaccording to

${d_{eSSS}( {2n} )} = \{ {\begin{matrix}{{{s_{0}^{(m_{0})}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 8},9,0,1,2} \\{{{s_{1}^{(m_{1})}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 3},4,5,6,7}\end{matrix},{{d_{eSSS}( {{2n} + 1} )} = \{ \begin{matrix}{{{s_{1}^{(m_{1})}(n)}{z_{1}^{(m_{0})}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 8},9,0,1,2} \\{{{s_{0}^{(m_{0})}(n)}{z_{1}^{(m_{1})}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 3},4,5,6,7}\end{matrix} }} $

where 0≤n≤30, and m₀, m₁, s₀ ^((m) ⁰ ⁾(n), s₁ ^((m) ¹ ⁾(n), z₁ ^((m) ⁰⁾(n), and z₁ ^((m) ¹ ⁾(n) are same as the ones in generating SSS.d_(eSSS) (n) is mapped in the frequency-domain to the center 62 REswithin the synchronization transmission bandwidth.

In some embodiments, the sequence to generate eSSS is similar to thesequence to generate SSS (given by the combination of two length-31sequences), but using different M-sequences such that thecross-correlation among SSS and eSSS is small. For example, theconstruction of sequence to generate eSSS can be according to

${d_{eSSS}( {2n} )} = \{ {{\begin{matrix}{{{s_{0}^{(m_{0})}(n)}{c_{0}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 8},9,0,1,2} \\{{{s_{1}^{(m_{1})}(n)}{c_{0}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 3},4,5,6,7}\end{matrix}m},{{d_{eSSS}( {{2n} + 1} )} = \{ \begin{matrix}{{{s_{1}^{(m_{1})}(n)}{c_{1}(n)}{z_{1}^{(m_{0})}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 8},9,0,1,2} \\{{{s_{0}^{(m_{0})}(n)}{c_{1}(n)}{z_{1}^{(m_{1})}(n)}\mspace{14mu} {in}\mspace{14mu} {subframes}\mspace{14mu} 3},4,5,6,7}\end{matrix} }} $

where 0≤n≤30, and m₀, m₁, s₀ ^((m) ⁰ ⁾(n) s₁ ^((m) ¹ ⁾(n), z₁ ^((m) ⁰⁾(n), and z₁ ^((m) ⁰ ⁾(n) are same as the ones in generating SSS, but{tilde over (s)}(n), {tilde over (c)}(n), {tilde over (z)}(n) aredifferent M-sequence with length-31. d_(eSSS)(n) is mapped in thefrequency-domain to the center 62 REs within the synchronizationtransmission bandwidth.

In some embodiments of component VIII for time-domain mapping of ePSS,the mapping of OFDM-symbol(s) containing ePSS in time-domain isillustrated. Note that the mapping can be combined with design optionsof ePSS sequence. The following design aspects are considered fortime-domain mapping of ePSS symbol, and their combinations are alsosupported in this disclosure.

In one embodiment of design aspect 1 for periodicity of ePSS or a set ofePSSs, analog to PSS, ePSS or a set of ePSSs can be transmittedperiodically. In one example, the periodicity of ePSS or a set of ePSSscan be the same as PSS (i.e., 5 ms). In another example, the periodicityof ePSS or a set of ePSSs can be twice of PSS (i.e., 10 ms), where ePSSor a set of ePSSs can be transmitted only in the first 5 ms of theperiodicity, or only in the second 5 ms of the periodicity, or in both 5ms periods within the periodicity but using different location or OCC(if multiplexed with other signal in the same symbol).

In one embodiment of design aspect 2 for number of symbols containingePSS within the periodicity, the number of ePSSs may depend on therequirement of latency enhancement for MTC. In one embodiment, there isonly one symbol containing ePSS within the periodicity (e.g. 1 ePSS in 5ms or 10 ms). In another embodiment, there are two symbols containingePSS within the periodicity (e.g. 2 ePSSs in 5 ms or 10 ms). In yetanother embodiment, there are three symbols containing ePSS within theperiodicity (e.g. 3 ePSSs in 5 ms or 10 ms). In yet another embodiment,there are four symbols containing ePSS within the periodicity (e.g. 4ePSSs in 5 ms or 10 ms). In yet another embodiment, there are eightsymbols containing ePSS within the periodicity (e.g. 8 ePSSs in or 10ms).

In one embodiment of design aspect 3, it is considered that whether ePSSor a set of ePSSs have the same relative location(s) in time-domaincomparing to PSS for TDD and FDD modes. Note that traditional UE usesthe relative location of PSS and SSS to blindly decode TDD or FDD.Hence, in one example, ePSS or a set of ePSSs have the same relativelocation(s) in time-domain comparing to PSS for TDD and FDD modes, thenLC-UE cannot utilize the location(s) of ePSS or a set of ePSSs toblindly decode TDD or FDD, and still use relative location of PSS andSSS to blindly decode TDD or FDD. In such example, the detectioncomplexity of ePSS is lower (no TDD or FDD hypothesis). In anotherexample, ePSS or a set of ePSSs have the different relative location(s)in time-domain comparing to PSS for TDD and FDD modes, then LC-UE canutilize the different location(s) of ePSS or a set of ePSSs to blindlydecode TDD or FDD, in addition to utilize the relative location of PSSand SSS. In such example, the detection complexity of ePSS is higher(one more hypothesis of TDD or FDD).

In one embodiment of design aspect 4 for a location of ePSS or a set ofePSSs, ePSS can be mapped to symbols which are utilized for downlinkdata transmission and do not contain CRS or DMRS. In this embodiment, aneNB needs to notify the traditional UE those symbols are reserved forePSS. In another embodiment, ePSS can be mapped to symbols which areutilized for LC-MIB transmission and do not contain CRS or DMRS. In thisembodiment, a set of ePSSs are multiplexed with repeated symbols forLC-MIB transmission using OCC (note that ePSSs are multiplexed with thesame repeated symbols for LC-MIB). In yet another embodiment, a set ofePSSs can be transmitted using patterns in both above embodiments. Forexample, part of the ePSSs are transmitted in symbols for downlink datatransmission, the remaining are transmitted in LC-MIB symbols using OCC.

In some embodiments of component IX for time-domain mapping of eSSS, themapping of OFDM-symbol(s) containing eSSS in time-domain is illustrated.Note that the mapping can be combined with design options of eSSSsequence. The following design aspects are considered for time-domainmapping of eSSS symbol, and their combinations are also supported inthis disclosure.

In one embodiment of design aspect 1 for periodicity of eSSS, analog toSSS, eSSS can be transmitted periodically (although the sequence of SSSis different for the first and second 5 ms within a frame). In oneembodiment, the periodicity of eSSS can be the same as SSS (i.e., 5 ms).In another embodiment, the periodicity of eSSS can be twice of SSS(i.e., 10 ms), where eSSS can be transmitted only in the first 5 ms ofthe periodicity, or only in the second 5 ms of the periodicity, or inboth 5 ms periods within the periodicity but using different location orOCC. Note that the periodicity of eSSS can be the same as ePSS, or canbe different from ePSS.

In one embodiment of design aspect 2 for a number of symbols containingeSSS within the periodicity, the number of eSSSs may depend on therequirement of latency enhancement (especially for cell ID) for MTC. Inone embodiment, there is only one symbol containing eSSS within theperiodicity (e.g. 1 eSSS in 5 ms or 10 ms). In another embodiment, thereare two symbols containing eSSS within the periodicity (e.g. 2 eSSS in 5ms or 10 ms). In yet another embodiment, there are three symbolscontaining eSSS within the periodicity (e.g. 3 eSSS in 5 ms or 10 ms).In yet another embodiment, there are four symbols containing eSSS withinthe periodicity (e.g. 4 eSSS in 5 ms or 10 ms). In yet anotherembodiment, there are eight symbols containing eSSS within theperiodicity (e.g. 8 eSSS in or 10 ms). Note that the number of eSSS canbe the same as ePSS (one-to-one mapping of eSSS and sPSS), or can bedifferent from eSSS (e.g. less than the number of ePSS).

In one embodiment of design aspect 3, it is considered that whether eSSSor a set of eSSSs have the same relative location(s) in time-domaincomparing to SSS for TDD and FDD modes. Note that traditional UE usesthe relative location of PSS and SSS to blindly decode TDD or FDD.Hence, in one embodiment, eSSS or a set of eSSSs have the same relativelocation(s) in time-domain comparing to SSS for TDD and FDD modes, thenLC-UE cannot utilize the location(s) of eSSS or a set of eSSSs to detectTDD or FDD, and still use relative location of PSS and SSS to blindlydecode TDD or FDD.

In another embodiment, eSSS or a set of eSSSs have the differentrelative location(s) in time-domain comparing to SSS for TDD and FDDmodes, then LC-UE can utilize the different location(s) of eSSS or a setof eSSSs to help detecting TDD or FDD, in addition to utilize therelative location of PSS and SSS. Note that whether the relativelocation of eSSS(s) and SSS is the same can be independent of whetherthe relative location of ePSS(s) and PSS is the same for TDD and FDD.For example, the relative location of ePSS(s) and PSS is the same forTDD and FDD, but the relative location of eSSS(s) and SSS is thedifferent for TDD and FDD.

In one embodiment of design aspect 4 for a location of eSSS or a set ofeSSSs, eSSS can be mapped to symbols which are utilized for downlinkdata transmission and do not contain CRS or DMRS. In this embodiment,eNB needs to notify the traditional UE those symbols are reserved foreSSS. In another embodiment, eSSS can be mapped to symbols which areutilized for LC-MIB transmission and do not contain CRS or DMRS. In thisembodiment, a set of eSSSs are multiplexed with repeated symbols forLC-MIB transmission using OCC (note that eSSSs are multiplexed with thesame repeated symbols for LC-MIB). In yet another embodiment, a set ofeSSSs can be transmitted using patterns in both above embodiments.

For example, part of the eSSSs are transmitted in symbols for downlinkdata transmission, the remaining are transmitted in LC-MIB symbols usingOCC. Note that the determination of eSSS location can be independent ofePSS. For example, ePSS and eSSS have one-to-one mapping relationship,where ePSS is mapped to symbol for data transmission, but eSSS is OCCwith LC-MIB symbol; or ePSS is OCC with LC-MIB symbol, but eSSS ismapped to symbol for data transmission.

In some embodiments of component X for ePSS and eSSS forResynchronization and Wake-up, another scenario considered is the systemacquisition with some apriori information. Different from initial cellsearch, UE may already have some system information known before gettingunsynchronized. In this scenario, the UE may rely on the so-calledre-synchronization signals (RSS) to get synchronized again, where theapriori information available at the UE can help with there-synchronization procedure.

In LTE, PSS and SSS are transmitted every 5 ms within the central 6PRBs, and their performance in the coverage-limited scenario may requiresignificant number of combinations for reliable synchronization. Forre-synchronization purpose, even though the apriori information, e.g.rough timing information and cell ID, can help with getting synchronizedto the system, fully relying PSS and SSS with very sparse transmissionin time-domain may not be sufficient. Hence, new always-on signals forthe re-synchronization purpose may be introduced.

Note that the introduction of the re-synchronization signals should notimpact the performance of legacy UEs in initial access. In oneembodiment, re-synchronization signals can avoid using the central 6PRBs for transmission. In another embodiment, re-synchronization signalscan be transmitted at any location in the frequency domain, and there-synchronization signals are with zero or little correlation withexisting PSS sequences in the system to avoid the timing ambiguity issuefor legacy UEs. In yet another embodiment, re-synchronization signalsare restricted to be transmitted in the central 6 PRBs in the frequencydomain, and the re-synchronization signals are with zero or littlecorrelation with existing PSS sequences in the system to avoid thetiming ambiguity issue for legacy UEs. Note that in this way, there-synchronization signals can also be utilized for initial accessenhancement if UEs know the time-domain configuration of there-synchronization signals.

The re-synchronization signals can be transmitted on one or multiple(consecutive) subframes, wherein the re-synchronization signals withineach subframe is considered as a design unit. In one embodiment,re-synchronization signals are only responsible for timing and frequencysynchronization, and no cell ID information is carried. For example, ineach design unit of RSS (e.g. a subframe), one or multiple OFDM symbolswithin the 6 PRBs are mapped for ePSS sequences. One further variant ofthis example is, an OCC can be applied to the symbols mapped for ePSSsequences, where the OCC may contain few bits of information indicatedto the UE, e.g. some simple system information update or an indicationof the system information update.

In another embodiment, re-synchronization signals are responsible fortiming and frequency synchronization, as well as confirmation of cell IDinformation. For example, in each design unit of RSS (e.g. a subframe),one or multiple OFDM symbols within the 6 PRBs are mapped for ePSSsequences, and one or multiple OFDM symbols within the 6 PRBs are mappedfor eSSS sequences, where the eSSS sequences can carry the whole or partof the cell ID information. One further variant of this example is, anOCC can be applied to the symbols mapped for ePSS sequences and/or eSSSsequences, where the OCC may contain few bits of information indicatedto the UE, e.g. some simple system information update or an indicationof the system information update.

The re-synchronization signals can be transmitted on one or multiple(consecutive) subframes in time domain. In one embodiment, the designunit of RSSs is repeated across all the transmitted subframes. Inanother embodiment, OCC is applied to the design units of RSSs acrossall or part of the transmitted subframes, where the OCC may contain fewbits of information indicated to the UE, e.g. some simple systeminformation update or an indication of the system information update.

The transmission of the re-synchronization signals follows predefinedpatterns in time domain. In one embodiment, the time-domain pattern isfixed, in term of the subframe indices for RSSs and periodicity of RSSs.In another embodiment, the time-domain pattern is configurable, whereeach configuration contains the information of subframe indices for RSSsand periodicity of RSSs. The configuration is performed at the NW end inorder to adjust the overhead of re-synchronization signals and toguarantee the one-shot detection performance of re-synchronizationsignals and UE needs to blind detect.

In yet another embodiment, the time-domain pattern is configurable,where each configuration contains the information of subframe indicesfor RS Ss and periodicity of RSSs. One of the configurations is bydefault in the spec and known at the UE end such that UE can utilizethis pattern for initial access enhancement.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

None of the description in this application should be read as implyingthat any particular element, step, or function is an essential elementthat must be included in the claims scope. The scope of patented subjectmatter is defined only by the claims. Moreover, none of the claims areintended to invoke 35 U.S.C. § 112(f) unless the exact words “means for”are followed by a participle.

What is claimed is:
 1. A user equipment (UE) in a wireless communicationsystem, the UE comprising: a transceiver configured to receive, from abase station (BS), re-synchronization signals (RSSs) over a downlinkchannel; and a processor operably connected to the transceiver, theprocessor configured to: identify time-domain and frequency-domainresources used for the RSSs; and identify a set of sequences used forconstructing the RSSs from the time-domain and frequency-domainresources used for the RSSs.
 2. The UE of claim 1, wherein the RSSs areperiodically received with at least one of a fixed or a configurableperiodicity, the at least one of the fixed or the configurableperiodicity being associated with a configuration of a discontinuousreception or extended discontinuous reception (DRX/eDRX) cycle ofpaging.
 3. The UE of claim 1, wherein a duration of the RSSs isdetermined as at least one subframe within a periodicity, the durationbeing associated with a configuration of a number of repetitions for amachine-type-communication physical downlink control channel (MPDCCH)transmission.
 4. The UE of claim 1, wherein the RSSs are identifiedbased on a construction unit of one subframe, and wherein at least onesymbol within the construction unit is mapped for at least one ofenhanced primary synchronization signals (ePSSs) or enhanced secondarysynchronization signals (eSSSs).
 5. The UE of claim 4, wherein the atleast one of the ePSSs or eSSSs is responsible for at least one of atime-domain re-synchronization, a frequency-domain re-synchronization,or a cell ID delivery.
 6. The UE of claim 4, wherein a subframe-levelcover code is applied to the at least one construction unit within aperiodicity, the subframe-level cover code being at least one of fixedor varying over time.
 7. The UE of claim 4, wherein at least one of: afirst symbol-level cover code is applied to the at least one symbolmapped for the ePSSs within the construction unit, the firstsymbol-level cover code being at least one of fixed or varying overtime; or a second symbol-level cover code is applied to the at least onesymbol mapped for the eSSSs within the construction unit, the secondsymbol-level cover code being at least one of fixed or varying overtime.
 8. A base station (BS) in a wireless communication system, the BScomprising: a processor configured to: configure time-domain andfrequency-domain resources used for re-synchronization signals (RSSs);generate a set of sequences to construct the RSSs; and map the generatedset of sequences to the time-domain and frequency-domain resources to beused for the RSSs; and a transceiver operably connected to theprocessor, the transceiver configured to transmit, to a user equipment(UE), the RSSs over a downlink channel.
 9. The BS of claim 8, whereinthe RSSs are periodically transmitted with at least one of a fixed or aconfigurable periodicity, the at least one of the fixed or theconfigurable periodicity being associated with a configuration of adiscontinuous reception or extended discontinuous reception (DRX/eDRX)cycle of paging.
 10. The BS of claim 8, wherein a duration of the RSSsis determined as at least one subframe within a periodicity, theduration being associated with a configuration of a number ofrepetitions for a machine-type-communication physical downlink controlchannel (MPDCCH) transmission.
 11. The BS of claim 8, wherein the RSSsare identified based on a construction unit of one subframe, and whereinat least one symbol within the construction unit is mapped for at leastone of enhanced primary synchronization signals (ePSSs) or enhancedsecondary synchronization signals (eSSSs).
 12. The BS of claim 11,wherein the at least one of the ePSSs or eSSSs is responsible for atleast one of a time-domain re-synchronization, a frequency-domainre-synchronization, or a cell ID delivery.
 13. The BS of claim 11,wherein a subframe-level cover code is applied to the at least oneconstruction unit within a periodicity, the subframe-level cover codebeing at least one of fixed or varying over time.
 14. The BS of claim11, wherein at least one of: a first symbol-level cover code is appliedto the at least one symbol mapped for the ePSSs within the constructionunit, the first symbol-level cover code being at least one of fixed orvarying over time; or a second symbol-level cover code is applied to theat least one symbol mapped for the eSSSs within the construction unit,the second symbol-level cover code being at least one of fixed orvarying over time.
 15. A method for a user equipment (UE) in a wirelesscommunication system, the method comprising: receiving, from a basestation (BS), re-synchronization signals (RSSs) over a downlink channel;identifying time-domain and frequency-domain resources used for theRSSs; and identifying a set of sequences used for constructing the RSSsfrom the time-domain and frequency-domain resources used for the RSSs.16. The method of claim 15, wherein the RSSs are periodically receivedwith at least one of a fixed or a configurable periodicity, the at leastone of the fixed or the configurable periodicity being associated with aconfiguration of a discontinuous reception or extended discontinuousreception (DRX/eDRX) cycle of paging.
 17. The method of claim 15,wherein a duration of the RSSs is determined as at least one subframewithin a periodicity, the duration being associated with a configurationof a number of repetitions for a machine-type-communication physicaldownlink control channel (MPDCCH) transmission.
 18. The method of claim15, wherein the RSSs are identified based on a construction unit of onesubframe, and wherein at least one symbol within the construction unitis mapped for at least one of enhanced primary synchronization signals(ePSSs) or enhanced secondary synchronization signals (eSSSs).
 19. Themethod of claim 18, wherein the at least one of the ePSSs or eSSSs isresponsible for at least one of a time-domain re-synchronization, afrequency-domain re-synchronization, or a cell ID delivery, and whereina subframe-level cover code is applied to the at least one constructionunit within a periodicity, the subframe-level cover code being at leastone of fixed or varying over time.
 20. The method of claim 18, whereinat least one of: a first symbol-level cover code is applied to the atleast one symbol mapped for the ePSSs within the construction unit, thefirst symbol-level cover code being at least one of fixed or varyingover time; or a second symbol-level cover code is applied to the atleast one symbol mapped for the eSSSs within the construction unit, thesecond symbol-level cover code being at least one of fixed or varyingover time.